RT Journal Article SR Electronic T1 Health effects of shift work and extended hours of work JF Occupational and Environmental Medicine JO Occup Environ Med FD BMJ Publishing Group Ltd SP 68 OP 72 DO 10.1136/oem.58.1.68 VO 58 IS 1 A1 Harrington, J M YR 2001 UL http://oem.bmj.com/content/58/1/68.abstract AB