( ( graphs ( of circles ) ) ; )
(ROOT (NP (NP (NNS graphs)) (PP (IN of) (NP (NNS circles))) (: ;)))
graphs of circles;
(ROOT (S (NP (NNP Circle) (NNS graphs)) (VP (VBP are) (ADJP (JJ useful) (PP (IN for) (S (VP (VBG showing) (NP (NP (NNS percents)) (PP (IN of) (NP (DT a) (NN whole))))))))) (. .)))