[en] [Gutenberg 41697] • Merck's 1899 Manual of the Materia Medica Merck & Co.
[en] Google · the Missing Manual O'Reilly Media
[en] [Gutenberg 53139] • Maxims and Instructions for the Boiler Room / Useful to Engineers, Firemen Relating to Steam Generators, Pumps, Appliances, Steam Heating, Practical Plumbing, etc. Createspace Independent Publishing Platform
[en] [Gutenberg 30557] • LILRC Interlibrary Loan Manual: January, 1976 Public Domain Books