The International Encyclopedia of Dance is available in both physical and ebook form. The physical copy is found in the reference collection across from the circulation desk, under call number Ref. GV1585.I586 1998. Because it's a reference book, it doesn't circulate, so you'll have to use it in the library.
To access the ebook version, do a Quick Search for its title with the dropdown set to Everything (the SUNY Potsdam Library Catalog option only searches our physical collection, so ebooks won't show up that way), and then click the Available Online link. Once you've accessed the Encyclopedia, be sure to use the Search Within Work field about halfway down on the left side, not the search bar at the top right, which searches the entire Oxford Reference collection, not the Encyclopedia itself.
You can access the other recommended encyclopedias, including American Decades, the Encyclopedia of World Biography, and many others, through the Gale Ebooks database. You can find it in the dropdown box located under Databases on the library's front page.
You can do a search for your choreographer from the Basic Search field at the top left of the database, which will pull up any article in which they appear in all the different encyclopedias available.