I'm at work on a MG fantasy which will feature a confrontation with some giant beavers (a semi-magical version of beavers, actually, from a "fairy world" which fled into early medieval Britain to escape some trouble in Faerie). In the story, the MC has to deal with these beavers, who are building a dam that threatens to flood the area (including some human settlements) - with an additional complication; the beavers aren't malevolent, they're just building the dam for the regular reasons beavers build dams and look upon the consequences for the local humans as "not our problem".

I'd like a few good non-fiction books on beavers to consult in depicting the beavers with as much accuracy as I can (taking into account that they're a fantastic variety of beaver). Can anyone here recommend any titles?