The unbounded dependency corpus of <cite>Rimell et al. (2009)</cite> includes seven grammatical constructions: object extraction from a relative clause (ObRC), object extraction from a reduced relative clause (ObRed), subject extraction from a relative clause (SbRC), free relatives (Free), object questions (ObQ), right node raising (RNR), and subject extraction from an embedded clause (SbEm), all chosen for being relatively frequent and easy to identify in PTB trees.