However, despite exhaustive research, I am reluctantly forced to resort to the familiar lexical locution, `Source unknown.
( However ( , ( ( despite ( exhaustive research ) ) ( , ( I ( ( ( am reluctantly ) ( forced ( to ( ( ( ( resort ( to ( the ( ( familiar lexical ) locution ) ) ) ) , ) ` ) ( Source unknown ) ) ) ) ) . ) ) ) ) ) )
(ROOT (S (ADVP (RB However)) (, ,) (PP (IN despite) (NP (JJ exhaustive) (NN research))) (, ,) (NP (PRP I)) (VP (VBP am) (ADVP (RB reluctantly)) (VP (VBN forced) (S (VP (TO to) (VP (VB resort) (PP (TO to) (NP (DT the) (ADJP (JJ familiar) (JJ lexical)) (NN locution))) (, ,) (`` `) (NP (NN Source) (NN unknown))))))) (. .)))
I have spent three days trying to find the original source.
( I ( ( have ( spent ( ( three days ) ( trying ( to ( find ( the ( original source ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (PRP I)) (VP (VBP have) (VP (VBN spent) (NP (NP (CD three) (NNS days)) (VP (VBG trying) (S (VP (TO to) (VP (VB find) (NP (DT the) (JJ original) (NN source))))))))) (. .)))