A tale of two countries: The Craig–Sakamoto–Matusita theorem

This paper has a long history. Junjiro Ogawa and I have been friends and collaborators for many years. We started this joint paper in the early 1990s and prepared a draft in September 1995. However, we were trying to improve and simplify some of the proofs, and we revised the paper in January 1998. But circumstances were such that we did not submit the paper, but planned to find further simplifications. Junjiro's untimely death in 2003 brought it forth again. Junjiro always liked this topic, and I am pleased to submit this joint paper in his memory. This paper contains both an historical summary as well as several new results. (Ingram Olkin)