There is still some controversy over the amount of influence that Xerox's PARC work, as opposed to previous academic research, had on the GUIs of the Apple Lisa and Macintosh, but it is clear that the influence was extensive, because first versions of Lisa GUIs even lacked icons. These prototype GUIs are at least mouse-driven, but completely ignored the WIMP ( "window, icon, menu, pointing device") concept. Screenshots of first GUIs of Apple Lisa prototypes show the early designs. Apple engineers visited the PARC facilities (Apple secured the rights for the visit by compensating Xerox with a pre-IPO purchase of Apple stock) and a number of PARC employees subsequently moved to Apple to work on the Lisa and Macintosh GUI. However, the Apple work extended PARC's considerably, adding manipulatable icons, and drag and drop manipulation of objects in the file system (see Macintosh Finder) for example. A list of the improvements made by Apple, beyond the PARC interface, can be read at Folklore.org. Jef Raskin warns that many of the reported facts in the history of the PARC and Macintosh development are inaccurate, distorted or even fabricated, due to the lack of usage by historians of direct primary sources.