Reference sources available online. For engineers, the most common sort of "reference book" would be a Handbook -- its a collection of facts and figures, not something you would read through, just refer to, to get the fact that you need -- physical properties (the boiling point of methane), chemical formulas, definitions, and more.
Textbooks and encyclopedia-style sources available online.
Some printed reference books still provide essential information. These are found on the shelves on the Main Floor of the Library.
The Knovel Digital Library is a collection of over 700 technical manuals, handbooks, and reference books on every aspect of engineering. It includes book chapters, interactive charts and graphs, formulas and equations, physical properties and constants that a scientist or engineer might need. Start your search here: