Yah sports reference is nice but statsheet was really cool. You could track which players were in the game together and their plus minus numbers during those minutes. Trying to track the stat when subs play a lot of minutes together in the second half is not really telling a lot.
Sports reference does the box plus minus under advanced stats but it's almost useless really. I wish statsheet was still around.
Under advanced stats they (sports reference) also do PER, win shares, efg percentage, and many others. It's about as good as it gets really. Statsheet was really nice for plus minus.