These are particularly tricky when short words, like articles or pronouns, are 
( These ( are ( particularly ( tricky ( when ( ( short words ) ( , ( ( like ( ( articles or ) pronouns ) ) ( , are ) ) ) ) ) ) ) ) )
(ROOT (S (NP (DT These)) (VP (VBP are) (ADJP (RB particularly) (JJ tricky) (SBAR (WHADVP (WRB when)) (S (NP (JJ short) (NNS words)) (, ,) (PP (IN like) (NP (NNS articles) (CC or) (NNS pronouns))) (, ,) (VP (VBP are))))))))
Articles make these much easier to do.  
( Articles ( ( make ( these ( ( much easier ) ( to do ) ) ) ) . ) )
(ROOT (S (NP (NNPS Articles)) (VP (VBP make) (S (NP (DT these)) (ADJP (RB much) (JJR easier)) (S (VP (TO to) (VP (VB do)))))) (. .)))