you 'll know a star when you see one . 
(ROOT (S (NP (PRP you)) (VP (MD 'll) (VP (VB know) (NP (DT a) (NN star)) (SBAR (WHADVP (WRB when)) (S (NP (PRP you)) (VP (VBP see) (NP (CD one))))))) (. .)))
(ROOT (S (NP (PRP )) (VP (MD ) (VP (VB ) (NP (DT ) (NN )) (SBAR (WHADVP (WRB )) (S (NP (PRP )) (VP (VBP ) (NP (CD ))))))) (. )))