Martin Gardner (1914-2010) was a well-known American author on mathematics and the sciences, who also has written a substantial body of work on Oz and L. Frank Baum. His 1957 collaboration with Russel B. Nye, The Wizard of Oz and Who he Was, was one of the earliest serious considerations of the Oz mythos.
Gardner has also written a non-canonical novel, Visitors from Oz (1998). His essay collections The Night is Large (1997) and Are Universes Thicker than Blackberries? (2003) contain Oz-related material.
Gardner's The Annotated Alice (1960), his edition of Lewis Carroll's Alice's Adventures in Wonderland and Through the Looking Glass, was the inspiration and model for Michael Patrick Hearn's The Annotated Wizard of Oz.