There are many difficulties inherent in adducing citational evidence unsupported by frequency.
( There ( ( are ( ( many difficulties ) ( inherent ( in ( adducing ( ( citational evidence ) ( unsupported ( by frequency ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (EX There)) (VP (VBP are) (NP (NP (JJ many) (NNS difficulties)) (ADJP (JJ inherent) (PP (IN in) (S (VP (VBG adducing) (S (NP (JJ citational) (NN evidence)) (ADJP (JJ unsupported) (PP (IN by) (NP (NN frequency))))))))))) (. .)))
There are no difficulties supporting the frequency. 
( There ( ( are ( ( no difficulties ) ( supporting ( the frequency ) ) ) ) . ) )
(ROOT (S (NP (EX There)) (VP (VBP are) (NP (NP (DT no) (NNS difficulties)) (VP (VBG supporting) (NP (DT the) (NN frequency))))) (. .)))