[1] “Slips, Trips & Falls Identification and Prevention;” Occupational Safety and Health Administration; Sacramento, CA 2007; https://www.osha.gov/dte/grant_materials/fy07/sh-16625-07/slipstripsfalls.ppt

[2] Swinderman, Todd; Marti, Andrew D.; Marshall, Daniel: “Foundations for Conveyor Safety;” Martin Engineering, Section 1, pg. 14. Worzalla Publishing Company, Stevens Point, WI 2016. https://www.martin-eng.com/content/product/690/safety-book