Muromachi Period

I am researching the later part of the Muromachi period from
1439 to 1453 and am having trouble locating any in-depth
readings.
At the moment I am looking for information surrounding
Imagawa Noritada(1406-1441), in particular his associates and
death in 1441. I would be interested to know if he had any
involvement at the Yuuki Castle battles in 1441 or the
assassination of Shogun Yoshinori in the same year.

Any information including links and books, you could give me
would be most appreciated.

Ben.