izjasniti

1. (izjasniti se o + loc.) to state one's position; to speak one's mind
   Ministar još nije hteo da se izjasni o tome. — The minister has not wanted to comment on that yet.
   Molim vas da se izjasnite do petka. — Please state your position by Friday.
2. (izjasniti se kao / za) to declare oneself; to identify oneself
   Na popisu se izjasnio kao Srbin. — In the census he declared himself a Serb.
3. (za / protiv + acc. / gen.) to come out in favour of; to come out against
   Većina građana se izjasnila protiv novog projekta. — Most citizens came out against the new project.

In all these meanings se is obligatory: izjasniti se. Non-reflexive izjasniti meaning 'to explain, to clarify' is dated.