Gaya APA

PE, J, M, T., Hager, L, S. (2009). Excavation Systems Planning, Design, and Safety . United State: The McGraw-Hill companies, inc.

Gaya MLA

PE, Joe, M., Turner,., Hager, Larry, S.. "Excavation Systems Planning, Design, and Safety". United State: The McGraw-Hill companies, inc, 2009. Text.