[Michael] went to the park with his father, [Hugh]. [David] was unhappy with her son, [Michael], and his grades. She enlisted a tutor to help him. [Hugh] bought a new refrigerator for his mother [Frances].
('David', 'Frances')
[David] was unhappy with her son, [Michael], and his grades. She enlisted a tutor to help him. [Michael] went to the park with his father, [Hugh]. [Hugh] bought a new refrigerator for his mother [Frances].
[{('David', 'mother', 'Frances'): [('David', 'son', 'Michael'), ('Michael', 'grandmother', 'Frances')]}, {('Michael', 'grandmother', 'Frances'): [('Michael', 'father', 'Hugh'), ('Hugh', 'mother', 'Frances')]}]
['son', 'father', 'mother']