^ 1.01.1Morley, Deborah; Parker, Charles S. Understanding Computers: Today and Tomorrow, Introductory 15th. Cengage. 2014-04-16: 53–54. ISBN 9781285767307.
^Bartle, Richard. Designing Virtual Worlds. New Riders. 2003: 9–10, 741. ISBN 0-13-101816-7. [pp. 9-10] TinyMUD was deliberately intended to be distanced from the prevailing hack-and-slay AberMUD style, and the "D" in its name was said to stand for "Dimension" (or, occasionally, "Domain") rather than "Dungeon;" this is the ultimate cause of the MUD/MU* distinction that was to arise some years later. [pp. 741] The "D" in MUD stands for "Dungeon" [...] because the version of ZORK Roy played was a Fortran port called DUNGEN.
^Hahn, Harley. The Internet Complete Reference 2nd. Osborne McGraw-Hill. 1996: 553. ISBN 0-07-882138-X. [...] muds had evolved to the point where the original name was too confining, and people started to say that "MUD" stood for the more generic "Multi-User Dimension" or "Multi-User Domain".
^Bartle, Richard. Designing Virtual Worlds. New Riders. 2003: 3. ISBN 0131018167. Confusingly, although the term MUD applies to virtual worlds in general, the term MU* does not—it is used strictly for text-based worlds. The introduction of computer graphics into the mix therefore caused a second spate of naming, in order to make a distinction between graphical MUDs and text MUDs.