2024
De Simone B, Agnoletti V, Abu-Zidan FM, Biffl WL, Moore EE, Chouillard E, Coccolini F, Sartelli M, Podda M, Di Saverio S, Kaafarani H, Balogh ZJ, Bala M, Leppäniemi AK, Kirkpatrick AW, Pikoulis E, Rasa K, Rosato C, Sawyer R, Ansaloni L, de’Angelis N, Damaskos D, Stahel PF, Kluger Y, Coimbra R, The ORSA Collaborative, Catena F. The Operating Room management for emergency Surgical Activity (ORSA) study: a WSES international survey. Updates in Surgery 76:687-698, 2024
2023
Butterworth SA, Zivkovic I, Kim S, Afshar K. Major morbidity and mortality associated with delays to emergent surgery in children: a risk-adjusted analysis. Canadian Journal of Surgery 66:E123-E131, 2023
Jha RK, Gajpal Y, Chattopadhyay M, Yang X. Multiple operation theatre scheduling for mitigating the disturbance caused by emergency patients. Systems and Soft Computing 5:200058, 2023
Lepercq D, Gauss T, Godier A, Bellet J, Bouhours G, Bouzat P, Cailliau E, Cook F, David JS, Drame F, Gauthier M, Lamblin A, Pottecher J, Tavernier B, Garrigue-Huet D. Association of organizational pathways with the delay of emergency surgery. JAMA Network Open 6:e238145, 2023
Oliveira M, Bélanger V, Ruiz A, Santos D. A systematic literature review on the utilization of extended operating room hours to reduce surgical backlogs. Frontiers in Public Health 11:1118072, 2023
Schulz A, Fliedner M. Minimizing the expected waiting time of emergency jobs. Journal of Scheduling 26:147-167, 2023
Wong T, Quinlan AG, Sarraf E, Irwin B, Stanley A, Do HT, Novak DC, Tsai MH. The operational ramifications of a first-in first-out bump policy. Perioperative Care and Operating Room Management 30:100302, 2023
Zhu S, Fan W, Li X, Yang S. Ambulance dispatching and operating room scheduling considering reusable resources in mass-casualty incidents. Operational Research 23:34, 2023
Zhu S, Fan W, Yang S, Pardalos PM. Scheduling operating rooms of multiple hospitals considering transportation and deterioration in mass-casualty incidents. Annals of Operations Research 321:717-753, 2023
2022
Dexter F, Epstein RH, Marian AA.
Decision-making for end-of-day relief of anesthesiologists based on equity can decrease group productivity: Historical cohort study from a hospital with both anesthesia residents and nurse anesthetists.
Perioperative Care and Operating Room Management 26:100244, 2022
Makboul S, El Hilali Alaoui A. A metaheuristic method for solving an emergency problem. International Journal of Logistics Systems and Management 41:29-58, 2022
Matava C, So J, Williams RJ, Kelley S, ORRACLE-Xtra Group. A Canadian weekend elective pediatric surgery program to reduce the COVID-19–related backlog: operating room ramp-up after COVID-19 lockdown ends—Extra Lists (ORRACLE-Xtra) implementation study. JMIR Perioperative Medicine 5:e35584, 2022
Ong BS, Thomas R, Jenkins S. Introducing the "Twilight" operating room concept: a feasibility study to improve operating room utilization. Patient Safety in Surgery 16:23, 2022
Parmar D, Woodman M, Pandit JJ. A graphical assessment of emergency surgical list efficiency to determine operating theatre capacity needs. British Journal of Anaesthesia 128:574-583, 2022
2021
Althoff FC, Wachtendorf LJ, Rostin P, Santer P, Schaefer MS, Xu X, Grabitz SD, Chitilian H, Houle TT, Brat GA, Akeju O, Eikermann M. Effects of night surgery on postoperative mortality and morbidity: a multicentre cohort study. BMJ Quality and Safety 30:678-688, 2021
Dexter F, Epstein RH, Marian AA.
Sustained management of the variability in work hours among anesthesiologists providing patient care in operating rooms and not on call to work late if necessary.
Journal of Clinical Anesthesia 69:110151, 2021
Miao H, Wang JJ. Scheduling elective and emergency surgeries at shared operating rooms with emergency uncertainty and waiting time limit. Computers and Industrial Engineering 160:107551, 2021
Tsai SC, Yeh Y, Kuo CY. Efficient optimization algorithms for surgical scheduling under uncertainty. European Journal of Operational Research 293:579-593, 2021
Wang JJ, Miao H, Xu R. Surgical rescheduling problem with emergency patients considering participants’ dissatisfaction. Soft Computing 25:10749-10769, 2021
Xiao Y, Yoogalingam R. Reserved capacity policies for operating room scheduling. Operations Management Research 14:107-122, 2021
2020
Alimin NN, Rahmin NAA, Ibragimov G, Nazihah MA. Multi-start local search for online scheduling in parallel operating theatre. Advances in Mathematics: Scientific Journal 9:10915-10927, 2020
Yazdi M, Zandieh M, Haleh H. A mathematical model for scheduling elective surgeries for minimizing the waiting times in emergency surgeries. International Journal of Engineering 33:448-458, 2020
2019
Ahmed K, Zygourakis C, Kalb S, Pennington Z, Molina C, Emerson T, Theodore N. Protocol for urgent and emergent cases at a large academic level 1 trauma center. Cureus 11:e3973, 2019
Ali HH, Lamsali H, Othman SN. Operating rooms scheduling for elective surgeries in a hospital affected by war-related incidents. Journal of Medical Systems 43:139, 2019
Jenkins PC, Painter S, Bell TM, Kline JA, Zarzaur BL. The conference effect: National surgery meetings are associated with increased mortality at trauma centers without American College of Surgeons verification. PLoS One 14:e0214020, 2019
Jung KS, Pinedo M, Sriskandarajah C, Tiwari V. Scheduling elective surgeries with emergency patients at shared operating rooms. Production and Operations Management 28:1407-1430, 2019
Martinez-Millana A, Lizondo A, Gatta R, Vera S, Salcedo VT, Fernandez-Llatas C. Process mining dashboard in operating rooms: analysis of staff expectations with analytic hierarchy process. International Journal of Environmental Research and Public Health 16:199, 2019
O'Leary JD, Wunsch H, Leo AM, Levin D, Siddiqui A, Crawford MW. Hospital admission on weekends for patients who have surgery and 30-day mortality in Ontario, Canada: a matched cohort study. PLoS Medicine 16:e1002731, 2019
Rodriguez T, Wolf-Mandroux A, Soret J, Dagneaux L, Canovas F. Compared efficiency of trauma versus scheduled orthopaedic surgery operating rooms in a university hospital. Orthopaedics & Traumatology: Surgery & Research 105:179-183, 2019
Sunshine JE, Humbert AT, Booth B, Bowman SM, Bulger EM, Sharar SR. Frequency of operative anesthesia care after traumatic injury. Anesthesia & Analgesia 129:141-146, 2019
Vandenberghe M, De Vuyst S, Aghezzaf EH, Bruneel H. Surgery sequencing to minimize the expected maximum waiting time of emergent patients. European Journal of Operational Research 275:971-982, 2019
Yang N, Elmatite WM, Elgallad A, Gajdos C, Pourafkari L, Nader ND. Patient outcomes related to the daytime versus after-hours surgery: a meta-analysis. Journal of Clinical Anesthesia 54:13-18, 2019
2018
Caesar U, Karlsson J, Hansson E. Incidence and root causes of delays in emergency orthopaedic procedures: a single-centre experience of 36,017 consecutive cases over seven years. Patient Safety in Surgery 12:2, 2018
Dexter F, Epstein RH, Jarvie C, Thenuwara KN. At all hospitals in the State of Iowa over a decade, the number of cases performed during weekends or holidays increased approximately proportionally to the total caseload. Journal of Clinical Anesthesia 50:27-32, 2018
Joerger G, Rambourg J, Gaspard-Boulinc H, Conversy S, Bass BL, Dunkin BJ, Garbey M. A cyber-physical system to improve the management of a large suite of operating rooms. ACM Transactions on Cyber-Physical Systems 2:34, 2018
Morgan DJ, Ho KM, Kolybaba ML, Ong YJ, ANZICS Centre for Outcome and Resource Evaluation. Adverse outcomes after planned surgery with anticipated intensive care admission in out-of-office-hours time periods: a multicentre cohort study. British Journal of Anaesthesia 120:1420-1428, 2018
Redmann AJ, Robinette K, Myer CM 4th, de Alarcón A, Veid A, Hart CK. Association of reduced delay in care with a dedicated operating room in pediatric otolaryngology. JAMA Otolaryngology-Head & Neck Surgery 144:330-334, 2018
Smith SA, Yamamoto JM, Roberts DJ, Tang KL, Ronksley PE, Dixon E, Buie WD, James MT. Weekend surgical care and postoperative mortality: A systematic review and meta-analysis of cohort studies. Medical Care 56:121-129, 2018
Walmsley T, Schmitgen G, Carr S, Mortimer P, Garside J, Gillibrand W. Changing operating lists on the day of surgery: a service evaluation. Journal of Perioperative Practice 28:238-242, 2018
2017
Bhamra JS, Dhinsa BS, Patel S, Davies C, OLiver M. Does a dedicated orthopaedic day surgery list improve delivery of trauma services? Journal of Perioperative Practice 27:263-268, 2017
Brusalis CM, Shah AS, Luan X, Lutts MK, Sankar WN. A dedicated orthopaedic trauma operating room improves efficiency at a pediatric center. The Journal of Bone and Joint Surgery 99:42-47, 2017
Fitzgerald A, Wu Y. Beyond clinical priority: what matters when making operational decisions about emergency surgical queues? Australian Health Review 41:384-393, 2017
Gerami F, Saidi-Mehrabad M. Stochastic reactive scheduling model for operating rooms considering the moral and human virtues. Applied Ecology and Environmental Research 15:563-592, 2017
Katz JS, O'Callaghan PK, Patel DD, Peterson AM, Angermeier EW, Kokko KP. Personal economic impact of performing elective Saturday hand surgery. Current Orthopaedic Practice 28:489-491, 2017
Paine AN, Andritsos DA, Fitzgerald JR, Norotsky MC, Malhotra AK, Tsai MH. The operational impact of an acute care surgical service on operating room metrics. Perioperative Care & Operating Room Management 8:38-41, 2017
Persson M, Hvitfeldt-Forsberg H, Unbeck M, Sköldenberg OG, Stark A, Kelly-Pettersson P, Mazzocato P. Operational strategies to manage non-elective orthopaedic surgical flows: a simulation modelling study. BMJ Open 7:e013303, 2017
Williams JP, Spernaes I, Duff E, Argent M, Frankish J, Dinham H. Development and implementation of a theatre booking form and morning briefing meeting to improve emergency theatre efficiency. Journal of Perioperative Practice 27:217-224, 2017
2016
Dexter F, Epstein RH, Campos J, Dutton RP.
US national anesthesia workload on Saturday and Sunday mornings.
Anesthesia & Analgesia 123:1297-1301, 2016
Glance LG, Osler T, Li Y, Lustik SJ, Eaton MP, Dutton RP, Dick AW. Outcomes are worse in US patients undergoing surgery on weekends compared with weekdays. Medical Care 54:608-615, 2016
Isedale G, Harris I, Rider M. Improving hand surgery access and care through service redesign. ANZ Journal of Surgery 86:581-583, 2016
Runner R, Moore T Jr, Reisman W. Value of a dedicated Saturday orthopaedic trauma operating room. Journal of Orthopaedic Trauma 30:e24-29, 2016
Stepaniak PS, Dexter F.
Constraints on the scheduling of urgent and emergency surgical cases: surgeon, equipment, and anesthesiologist availability.
Perioperative Care and Operating Room Management 3:6-11, 2016
Traynor AJ, Aragon M, Ghosh D, Choi RS, Dingmann C, Vu Tran Z, Bucklin BA. Obstetric anesthesia workforce survey: a 30-year update. Anesthesia & Analgesia 122:1939-1946, 2016
van Veen-Berkx E, Elkhuizen SG, Kuijper B, Kazemier G; Dutch Operating Room Benchmarking Collaborative. Dedicated operating room for emergency surgery generates more utilization, less overtime, and less cancellations. The American Journal of Surgery 211:122-128, 2016
2015
Antognini JM, Antognini JF, Khatri V. How many operating rooms are needed to manage non-elective surgical cases? A Monte-Carlo simulation study. BMC Health Services Research 15:487, 2015
Beebe AC, Arnott L, Klamar JE, Kean JR, Klingele KE, Samora WP. Utilization of orthopaedic trauma surgical time: an evaluation of three different models at a Level 1 Pediatric trauma center. Orthopaedic Surgery 7:333-337, 2015
Mueller RN, Dexter F, Truong VA, Wachtel RE.
Case sequencing of diagnostic imaging studies performed under general anesthesia or monitored anesthesia care during nights and weekends.
A & A Case Reports 5:162-166, 2015
Roberts TT, Vanushkina M, Khasnavis S, Snyder J, Papaliodis DN, Rosenbaum AJ, Uhl RL, Roberts JT, Bagchi K. Dedicated orthopaedic operating rooms: beneficial to patients and providers alike. Journal of Orthopaedic Trauma 29:e18-23, 2015
Van Riet C, Demeulemeester E. Trade-offs in operating room planning for electives and emergencies: a review. Operations Research for Health Care 7:52-69, 2015
Wiyartanti L, Park MW, Chung D, Kim JK, Sohn YT, Kwon GH. Managing uncertainties in the surgical scheduling. Studies in Health Technology and Informatics 210:384-388, 2015
Zenteno AC, Carnes T, Levi R, Daily BJ, Price D, Moss SC, Dunn PF. Pooled open blocks shorten wait times for nonelective surgical cases. Annals of Surgery 262:60-67, 2015
2014
Ferrand YB, Magazine MJ, Rao US. Managing operating room efficiency and responsiveness for emergency and elective surgeries - a literature survey. IIE Transactions on Healthcare Systems Engineering 4:49-64, 2014
Ferrand YB, Magazine MJ, Rao US. Partially flexible operating rooms for elective and emergency surgeries. Decision Sciences 45:819-847, 2014
O'Leary DP, Beecher S, McLaughlin R. Emergency surgery pre-operative delays - realities and economic impacts. International Journal of Surgery 12:1333-1336, 2014
Rachuba S, Werners B. A robust approach for scheduling in hospitals using multiple objectives. Journal of the Operational Research Society 65:546-556, 2014
Remick KN, Schwab CW, Smith BP, Monshizadeh A, Kim PK, Reilly PM. Defining the optimal time to the operating room may salvage early trauma deaths. The Journal of Trauma and Acute Care Surgery 76:1251-1258, 2014
2013
Heng M, Wright JG. Dedicated operating room for emergency surgery improves access and efficiency. Canadian Journal of Surgery 56:167-174, 2013
Javed S, Peck C, Salthouse D, Woodruff MJ. A predetermined first patient on the trauma list can improve theatre start times. Injury 44:1528-1531, 2013
Leppäniemi A, Jousela I. A traffic-light coding system to organize emergency surgery across surgical disciplines. The British Journal of Surgery 101:e134-e140, 2013
Paul JA, MacDonald L. Determination of number of dedicated ORs and supporting pricing mechanisms for emergent surgeries. Journal of the Operational Research Society 64:912-924, 2013
Tancrez JS, Roland B, Cordier JP, Riane F. Assessing the impact of stochasticity for operating theater sizing. Decision Support Systems 55:616-628, 2013
2012
Erdem E, Qu X, Shi J. Rescheduling of elective patients upon the arrival of emergency patients. Decision Support Systems 54:551-563, 2012
van Essen JT, Hans EW, Hurink JL, Oversberg A. van Essen JT, Hans EW, Hurink JL, Oversberg A. Minimizing the waiting time for emergency surgery. Operations Research for Health Care 1:34-44, 2012
2011
Dhupar R, Evankovich J, Klune JR, Vargas LG, Hughes SJ. Delayed operating room availability significantly impacts the total hospital costs of an urgent surgical procedure. Surgery 150:299-305, 2011
Murray BW, Huerta S, Anthony T. A strategy for reducing surgical backlogs: lessons from a Veterans Administration hospital. The American Surgeon 77:597-601, 2011
Richardson JE, Shah-Hosseini S, Fiadjoe JE, Ash JS, Rehman MA. The effects of a hands-free communication device system in a surgical suite. Journal of the American Medical Informatics Association 18:70-72, 2011
2010
Bardram JE, Hansen TR. Context-based workplace awareness: Concepts and technologies for supporting distributed awareness in a hospital environment. Computer Supported Cooperative Work 19:105-138, 2010
Ledolter J, Dexter F, Wachtel RE.
Control chart monitoring of the numbers of cases waiting when anesthesiologists do not bring in members of call team.
Anesthesia & Analgesia 111:196-203, 2010
Tuggle D, Lucas CE, Coscia RL, Hurst JM, Meredith JW, Middleton JD, Rinker CR, Vlahos AL, Wilberger J. Mathematical modeling to define optimum operating room staffing for pediatric patients in trauma centers. Journal of Pediatric Surgery 45:2431-2435, 2010
Turrentine FE, Wang H, Young JS, Calland JF. What is the safety of nonemergent operative procedures performed at night? A study of 10,426 operations at an academic tertiary care hospital using the American College of Surgeons national surgical quality program improvement database. The Journal of Trauma: Injury, Infection, and Critical Care 69:313-319, 2010
Zonderland ME, Boucherie RJ, Litvak N, Vleggeert-Lankamp CL. Planning and scheduling of semi-urgent surgeries. Health Care Management Science 13:256-267, 2010
2009
Basso O. Cost analysis of a system of ad hoc theatre sessions for the management of delayed trauma cases. Journal of Orthopaedic Traumatology 10:91-96, 2009
Dexter F, Epstein RH, Elgart RL, Ledolter J.
Forecasting and perception of average and latest hours worked by on-call anesthesiologists.
Anesthesia & Analgesia 109:1246-1252, 2009
2008
Cosgrove JF, Gaughan M, Snowden CP, Lees T. Decreasing delays in urgent and expedited surgery in university teaching hospital through audit and communication between peri-operative and surgical directorates. Anaesthesia 63:599-603, 2008
Kim YJ, Xiao Y, Hu P, Dutton R. Staff acceptance of video monitoring for coordination: a video system to support perioperative situation awareness. Journal of Clinical Nursing 18:2366-2371, 2008
Testi A, Tanfani E, Valente R, Ansaldo GL, Torre GC. Prioritizing surgical waiting lists. Journal of Evaluation in Clinical Practice 14:59-64, 2008
van Oostrum JM, Van Houdenhoven M, Vrielink MM, Klein J, Hans EW, Klimek M, Wullink G, Steyerberg EW, Kazemier G. A simulation model for determining the optimal size of emergency teams on call in the operating room at night. Anesthesia & Analgesia 107:1655-1662, 2008
Xiao Y, Dexter F, Hu P, Dutton RP.
The use of distributed displays of operating room video when real-time occupancy status was available.
Anesthesia & Analgesia 106:554-560, 2008
2007
Dexter F, Willemsen-Dunlap A, Lee JD.
Operating room managerial decision-making on the day of surgery with and without computer recommendations and status displays.
Anesthesia & Analgesia 105:419-429, 2007
Faiz O, Banerjee S, Tekkis P, Papagrigoriadis S, Rennie J, Leather A. We still need to operate at night!. World Journal of Emergency Surgery 2:29, 2007
Wullink G, Houdenhoven M, Hans EW, Oostrum JM, Lans M, Kazemier G. Closing emergency operating rooms improves efficiency. Journal of Medical Systems 31:543-546, 2007
Xiao Y, Schenkel S, Faraj S, Mackenzie CF, Moss J. What whiteboards in a trauma center operating suite can teach us about emergency department communication. Annals of Emergency Medicine 50:387-395, 2007
2006
Bhattacharyya T, Vrahas MS, Morrison SM, Kim E, Wiklund RA, Smith RM, Rubash HE. The value of the dedicated orthopaedic trauma operating room. The Journal of Trauma 60:1336-1341, 2006
Dexter F, Epstein RH.
Holiday and weekend operating room on-call staffing requirements.
Anesthesia & Analgesia 103:1494-1498, 2006
Fitzgerald J, Lum M, Dadich A. Scheduling unplanned surgery: a tool for improving dialogue about queue position on emergency theatre lists. Australian Health Review 30:219-231, 2006
O’Sullivan CT, Dexter F. Assigning surgical cases with regional anesthetic blocks to anesthetists and operating rooms based on operating room efficiency. AANA Journal 74:213-218, 2006
St. Jacques PJ, France DJ, Pilla M, Lai E, Higgins MS. Evaluation of a hands-free wireless communication device in the perioperative environment. Telemedicine Journal and e-Health 12:42-49, 2006
Torkki PM, Alho AI, Peltokorpi AV, Torkki MI, Kallio PE. Managing urgent surgery as a process: case study of a trauma center. International Journal of Technology Assessment in Health Care 22:255-260, 2006
2005
Charalambous CP, Tryfonidis M, Paschalides C, Lamprianou I, Samarji R, Hirst P. Operating out of hours in acute orthopaedics: Variations amongst surgeons and regions in the United Kingdom. Injury 36:1306-1310, 2005
2004
Dexter F, Epstein RH, Traub RD, Xiao Y.
Making management decisions on the day of surgery based on operating room efficiency and patient waiting times.
Anesthesiology 101:1444-1453, 2004
Seagull FJ, Xiao Y, Plasters C. Information accuracy and sampling effort: a field study of surgical scheduling coordination. IEEE Transactions on Systems, Man and Cybernetics, Part A. 34:764-771, 2004
2003
Dexter F, Epstein RH. Optimizing second shift OR staffing. AORN Journal 77:825-830, 2003
2002
Conaghan PJ, Figueira E, Griffin MA, Ingham Clark CL. Randomized clinical trial of the effectiveness of emergency day surgery against standard inpatient treatment. British Journal of Surgery 89:423-427, 2002
Dexter F, Epstein RH, Marsh HM. Costs and risks of weekend anesthesia staffing at six independently managed surgical suites. AANA J 70:377-381, 2002
Windokun A, Obideyi A. Audit of emergency theatre utilisation. African Journal of Medicine & Medical Sciences 31:59-62, 2002
2001
Dexter F, O'Neill L. Weekend operating room on-call staffing requirements: schedule each staff member in-house or on standby from home? AORN Journal 74:666-671, 2001
Lucas CE, Buechter KJ, Coscia RL, Hurst JM, Meredith JW, Middleton JD, Rinker CR, Tuggle D, Vlahos AL, Wilberger J. Mathematical modeling to define optimum operating room staffing needs for trauma centers. Journal of the American College of Surgeons 192:559-565, 2001
Pearse RM, Dana EC, Lanigan CJ, Pook JA. Organisational failures in urgent and emergency surgery. A potential peri-operative risk factor. Anaesthesia 56:684-689, 2001
2000
Dexter F, Macario A, Traub RD. Statistical method using operating room information system data to determine anesthetist weekend call requirements. AANA Journal 68:21-26, 2000
Dexter F, Traub RD. Determining staffing requirements for a second shift of anesthetists by graphical analysis of data from operating room information systems. AANA Journal 68:31-36, 2000
Dexter F.
A strategy to decide whether to move the last case of the day in an operating room to another empty operating room to decrease overtime labor costs.
Anesthesia & Analgesia 91:925-928, 2000
1999
Dexter F, Macario A, O'Neill L.
A strategy for deciding operating room assignments for second-shift anesthetists.
Anesthesia & Analgesia 89:920-924, 1999
Dexter F, Macario A, Traub RD.
Which algorithm for scheduling add-on elective cases maximizes operating room utilization? Use of bin packing algorithms and fuzzy constraints in operating room management.
Anesthesiology 91:1491-1500, 1999
Dexter F, Macario A, Traub RD. Optimal sequencing of urgent surgical cases - scheduling cases using operating room information systems. Journal of Clinical Monitoring and Computing. 15:153-162, 1999
Tucker JB, Barone JE, Cecere J, Blabey RG, Rha CK. Using queueing theory to determine operating room staffing needs. Journal of Trauma- Injury, Infection, & Critical Care 46:71-77, 1999
1998
Zhou J, Dexter F.
Method to assist in the scheduling of add-on surgical cases - upper prediction bounds for surgical case durations based on the log normal distribution.
Anesthesiology 89:1228-1232, 1998
1997
Lucas CE, Dombi GW, Crilly RJ, Ledgerwood AM, Yu P, Vlahos A. Neurosurgical trauma call: use of a mathematical simulation program to define manpower needs. Journal of Trauma 42:818-824, 1997
Tessler MJ, Kleiman SJ, Huberman MM. A “zero tolerance for overtime” increases surgical per case costs. Canadian Journal of Anaesthesia 44:1036-1041, 1997
1996
Dexter F. Application of prediction levels to operating room scheduling. AORN Journal 63:607-615, 1996