( HOT-WATER ( HEATING ( BOILER - ) ) )
(ROOT (NP (NNP HOT-WATER) (NNP HEATING) (NNP BOILER) (: -)))
HOT-WATER HEATING BOILER -
(ROOT (S (NP (NP (DT The) (NN water)) (PP (IN in) (NP (DT some) (NNS springs)))) (VP (VBP are) (ADJP (JJ hot) (SBAR (IN because) (S (NP (PRP they)) (VP (VBP 're) (VP (VBN heated) (PP (IN by) (NP (JJ hot) (NN magma))))))))) (. .)))