N1Grammar- studying differences between similar expressions

Also good for disambiguation, Nihongo no Mori!
https://www.youtube.com/user/freejapanes.../playlists

I like どんなとき as a quick n' dirty reference, but I have to admit that when I'm totally lost, I go to 日本語文型辞典 for help. Also, くらべてわかる日本語表現文型辞典 is pretty useful, too.