[KyleGoetz]

I was flipping through my copy of NTC's 新漢字字典 and came across this:

勉める, usu. 努める
Is there a difference here like there is with 川・河 that has been covered here previously? I'd never even seen 勉める before! I'd always used 努める to write it.

I know that 勤める should be distinguished from those because they mean "to try hard" or "to make efforts," while the latter means "to be employed (by)."