Guide was developed by Peter Brown as a research project at the University of Canterbury, U.K. Later, it was commercially marketed by Office Workstations Limited both on the IBM PC and Apple Macintosh. It is the most popular commercial hypertext system. Text and graphics are integrated together in articles or documents. Guide supports four different kinds of links: replacement buttons, note buttons, reference buttons, and command buttons. Navigation through the replacement buttons initially provides a summary of the information and the degree of detail can be changed by the reader. Similar to KMS, Guide also does not distinguish between the author and the reader [Brown, 1987].