( X-rays ( ( ( differ ( from ( gamma rays ) ) ) ( only ( in ( how ( they ( are ( produced ( in ( the atom ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNS X-rays)) (VP (VBP differ) (PP (IN from) (NP (NN gamma) (NNS rays))) (ADVP (RB only) (PP (IN in) (SBAR (WHADVP (WRB how)) (S (NP (PRP they)) (VP (VBP are) (VP (VBN produced) (PP (IN in) (NP (DT the) (NN atom)))))))))) (. .)))
X-rays differ from gamma rays only in how they are produced in the atom.
(ROOT (S (NP (NP (JJ Radioactive) (NNS atoms)) (, ,) (NP (JJ nuclear) (NNS explosions)) (, ,) (CC and) (NP (NNS stars))) (VP (VBP produce) (NP (NN gamma) (NNS rays)))))
Radioactive atoms, nuclear explosions, and stars produce gamma rays