proves as clear and reliable an authority on that 
(ROOT (S (VP (VBZ proves) (NP (NP (ADJP (RB as) (JJ clear) (CC and) (JJ reliable)) (DT an) (NN authority)) (PP (IN on) (NP (DT that)))))))
(ROOT (S (VP (VBZ ) (NP (NP (ADJP (RB ) (JJ ) (CC ) (JJ )) (DT ) (NN )) (PP (IN ) (NP (DT )))))))