Note: The Huli-Jing (China) and Gumiho/Kumiho (Korea) are analogous to the Kitsune of Japan, but the specifics of their mythologies and how they are viewed differs between each culture.
Title
Descriptions/Notes
Author
Date of Publication
Reference
Kitsune: Japan's Fox of Mystery, Romance & Humor
Long out of print, but now available freely online here (Direct Link)
Kiyoshi Nozaki
1961
ISBN-10: 1933330341
Shifting Shape, Shaping Text - Philosophy and Folklore in the Fox Kòan
Fire and Femininity: Fox Imagery and Ethical Responsibility
This is the only English-language paper I'm aware of that references the work of Yoshino Hiroko, who previously wrote about the associations of kitsune with elemental types from Yin-Yang Philosophy. The Void (Ku or Mu) element is not discussed in the paper (You'll find that in Godai from Japanese Buddhist Philosophy.).
The oldest written record in Japan, compiled in 712. It records the Japanese imperial line as well as lineage of the Kami. The Chamberlain translation is the easiest to find translation, and can occasionally be found for ~$30USD on ebay.
Basil Chamberlain (transl)
2005
ISBN: 9780804836753
The Kojiki
Possibly-better translation without the rending into Latin of the racy parts, but it is exceptionally expensive in print form. It isn't too hard to find on the internet anyway, if you look for it..
Donald L. Phillipi
2016 (orig.1967)
IBSN-10: 0691648905
A Structural Reading of The Kojiki
An academic paper giving historical context to the stories and themes present within the Kojiki. It also contextualizes the Nihongi.
Also called The Nihon-Shoki, it was compiled in 720 and is considered to be a more factual account than the Kojiki. (Note: the index for both books is found only in the second volume.)