as clear and reliable an authority on that 
(ROOT (PP (IN as) (NP (NP (ADJP (JJ clear) (CC and) (JJ reliable)) (DT an) (NN authority)) (PP (IN on) (NP (DT that))))))
(ROOT (PP (IN ) (NP (NP (ADJP (JJ ) (CC ) (JJ )) (DT ) (NN )) (PP (IN ) (NP (DT ))))))