1. Roof holes are death traps;Barnhard;The Journeyman Roofer & Waterproofer,2001
2. Falls through Roof and Floor Openings and Surfaces, Including Skylights: 1992-2000;Bobick;Journal of Construction Engineering and Management,2004
3. Using Guardrail Systems to Prevent Falls Through Roof and Floor Holes;Bobick,2005
4. Fatal occupational injuries by event or exposure and major private industry division, All U.S., 2003 (Table A-9),2003
5. Number of non-fatal occupational injuries and illnesses involving days away from work by event or exposure leading to injury or illness and number of days away from work, 2003 (Table R70),2003