http://tags.library.upenn.edu/tag/guides+reference PennTags Feed http://tags.library.upenn.edu/makerecord/url/25781 http://tags.library.upenn.edu/makerecord/url/25781 http://tags.library.upenn.edu/makerecord/url/2271 http://tags.library.upenn.edu/makerecord/url/2271 Bibliographic citations for materials received at the Transportation Library, Northwestern University, since 1976.