For the first one, you may want to google "chess endgame database". First hit (using Ixquick, for me) is an online database where you can quickly confirm that 2 bishops vs. 2 knights is a draw (whereas K+B+B vs. K+N is won for the bishops).
I can't help you about the other two, but I think that searching more general terms might be better if you aren't certain how the professionals talk about the topic in question (e.g. "quantum number conversation").
that 2 bishops vs. 2 knights is a draw
There:
english.turkcebilgi.com/Bishop+(chess)
I found this:
...Bishops generally gain in relative strength towards the endgame as more pieces are captured and more open lines are available for them to operate. When the board is empty, a bishop can influence both wings simultaneously, whereas a knight would need a few moves to do so. In an open endgame, a pair of bishops is decidedly superior to either a bishop and a knight, or to two knights. A player possessing a pair of bishops has a strategic weapon in the form of a
Recently in another topic I mentioned the "two bishops against two knights" chess endgame problem. I claimed it was investigated over two decades ago by a computer program and established that it is a win situation for the two bishops' side. Then I was unable to Google a solid reference for my claim.
I also remember a "Hermes Set Theory". It was something like ZFC, regarded as a valid Set Theory axiom system for 40 years, until a paradox was found inside. Now, I can't Google it out.
And then it was the so called "Baryon number conservation law", which was postulated for a short while in physics. Until it was found that a subatomic decay may in fact in/decrease the number of baryons in the process. I can't Google that one either.
Is that just me, or what?