This article is from the Amiga Books FAQ, by Marc Atkin with numerous contributions by others.
o Motorola: Programmers Reference Manual [publisher?], 1992?. [ISBN?] document number: M68000PM/AD
email@example.com (Doug Keller), 31 Mar 1993: "If you want to know about the hardware get the 030 or 040 Users Manual from Motorola. If you want to know about assembly language programming get the Programmers Reference Manual. The Programmers Reference Manual covers all the processors in the 68000 series."
Charles_P_Peterson@fcircus.sat.tx.us (Charles P Peterson), 8 Jan 95: "This manual covers 68000-68040, 68881, 68882, 68851 (not 68060 yet). There is no programmer's manual for the 68060 yet (as of December 1994) just a `User's' manual. I just got [the Reference Manual], and it's a very nicely bound large and thick softcover book. Obviously a bargain, and a necessity for anyone doing this kind of work."
Thakeria@Delphi.com (Kenneth L. Young), 15 Mar 95: "The best source of information about instruction codes and timing sequences for the Motorola family of microprocessors that I have found is in a resource manual that Motorola publishes called M68000 Family Programmer's Reference Manual. [...] My catalog currently lists the cost at $3.70 plus shipping and handling. This is worth 500 times its weight in gold. This book also contains reference material for the `MC68330 - Integrated CPU32 Processor', `MC68340 - Integrated Processor with DMA', `MC68851 - Paged Memory Management Unit', `MC68881 - Floating-Point Coprocessor', and `MC68882 - Enhanced Floating-Point Coprocessor'."
firstname.lastname@example.org (Dirk Stoecker), 8 Jan 2001: "It is distributed as PDF and also sent for free if requested at Motorola web pages. Also there are books for 68000, 68020, 68040 and 68060."
o Motorola: MC68030 Users Manual [publisher?], 1990. [ISBN?] document number: MC68030UM/AD
Reid_Bishop@a68k.denver.CO.US (Reid Bishop), 31 Mar 93: "I think the best references are Motorola's own users manuals. I have the 68030 manual, and it is excellent."