I am working on an article with Tim Kiser and Cathy Hodge on map classification systems used by libraries and have a slight problem. As part of the article, we're including a brief description of the classification systems and how the call numbers work. So I know that for a topical map in Dewey, the notation .022 is added to the base number for say 386 for a map of ferry lines. That gives us a call number of 386.022 but how would I add the extension to show that it's a map of ferry lines in Michigan? Would it be 386.022774? None of us have worked with Dewey all that much and are hoping that someone more familiar with the system can point us in the right direction.

Many thanks!

Susan Moore

University of Northern Iowa

Cedar Falls, IA 50614