Talking to a colleague just ¡­

Talking to a colleague just now, I realize there are another two useful Lisp references, both available on-line for quick look-up of functions or various language concepts more generally: Common Lisp the Language (Second Edition) by Guy L. Steele Jr. strikes a good balance of language reference and (subtle) humor; the Common Lisp HyperSpec is less suited for reading, but much more densely linked.