(s(np(det_the)(n_woman))(vp(v_sees)(pp(p_in)(np(det_the)(n_house)))))
(s(np(det_the)(n_time))(vp(v_elapsed)))
(s(np(det_the)(adv_very)(adj_nice)(n_girl))(vp(v_is)(pp(p_my)(n_friend))))
(s(np(det_the)(n_girl))(vp(v_depends)(pp(p_on)(np(det_the)(n_boy)))))
This is an example of an invalid structure.  Its is not in correct form.
(s(np(np(det_the)(adj_large)(n_man))(pp(p_on)(np(det_the)(n_moon))))(vp(v_wore)(np(det_a)(adj_grey)(n_suit))))
(s(np(det_the)(n_girl))(vp(v_forgot)(np(det_the)(n_boy))))
(s(np(n_girls))(vp(v_put)(np(n_books))(pp(p_in)(np(n_houses)))))
(s(np(det_the)(n_girl))(vp(v_gives)(np(det_the)(n_truck))(pp(p_to)(np(det_the)(n_boy)))))
(s(np(det_a)(n_girl))(vp(v_put)(np(det_a)(n_book))(pp(p_in)(np(det_a)(n_house)))))
(s(np(n_girls))(vp(v_put)(np(n_books))(pp(p_in)(np(n_classrooms)))))