NFPA 1931 Standard for Manufacturer's Design of Fire Department Ground Ladders, 2004 ed. https://www.nfpa.org/assets/files/AboutTheCodes/19 32/1932-A2004-ROP.pdf, (Std: Mfg Design of Fr Dept Gr Ladr - Amer) {419 NFC}
Ralph W. Burklin & Robert G. Purington, Fire Terms: A Guide to Their Meaning and Use, National Protection Association, Boston, MA 1980 USA. (Guide: Meaning and Use, Nat Prot Association Fr Srvc - Amer) {457}