that serve no other purpose than to call attention to themselves 
(ROOT (SBAR (WHNP (DT that)) (S (VP (VBP serve) (NP (NP (DT no) (JJ other) (NN purpose)) (SBAR (IN than) (S (VP (TO to) (VP (VB call) (NP (NN attention)) (PP (IN to) (NP (PRP themselves))))))))))))
(ROOT (SBAR (WHNP (DT )) (S (VP (VBP ) (NP (NP (DT ) (JJ ) (NN )) (SBAR (IN ) (S (VP (TO ) (VP (VB ) (NP (NN )) (PP (IN ) (NP (PRP ))))))))))))