They should stand back <apostrophe><apostrophe>
(ROOT_0 (S_0 (ATS_2 (SBAR_0 (S_1 (NP_1 (PRP_0 They)) (VP_5 (MD_0 should) (VP_1 (VB_0 stand))))) (ADVP_0 (RB_0 back))) (APOSTROPHE_0 <apostrophe><apostrophe>)))