hard-to-predict and absolutely essential 
(ROOT (ADJP (ADJP (JJ hard) (HYPH -) (SBAR (S (VP (TO to) (HYPH -) (VP (VB predict)))))) (CC and) (ADJP (RB absolutely) (JJ essential))))
(ROOT (ADJP (ADJP (JJ ) (HYPH ) (SBAR (S (VP (TO ) (HYPH ) (VP (VB )))))) (CC ) (ADJP (RB ) (JJ ))))