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 should be considered when doing these.  
( Articles ( ( should ( be ( considered ( when ( doing these ) ) ) ) ) . ) )
(ROOT (S (NP (NNPS Articles)) (VP (MD should) (VP (VB be) (VP (VBN considered) (SBAR (WHADVP (WRB when)) (S (VP (VBG doing) (NP (DT these)))))))) (. .)))