Tanka Resources
There are many excellent books and other sources of information about tanka. These are just a few of my personal favourites.
Michael Dylan Welch has an extensive collection of essays here: https://www.graceguts.com/tanka
My favourite book of Japanese tanka is Modern Japanese Tanka edited and translated by Makoto Ueda:
https://www.amazon.co.uk/Modern-Japanese-Tanka-Anthology-Literature/dp/0231104332
My favourite book of English language tanka is The Tanka Anthology edited by Michael McClintock, and not just because I have some tanka in it!
https://www.amazon.co.uk/Tanka-Anthology-English-finest-practioners/dp/1893959406
I have also written a couple of articles relating to tanka.
Tanka, the muse and the male muse. Originally published in Presence. https://haikusoup.blogspot.com/2020/02/tanka-muse-and-male-muse.html
Why I write both haiku and tanka. Originally published in Blithe Spirit. https://haikusoup.blogspot.com/2020/09/why-i-write-both-haiku-and-tanka.html