Why is it so difficult to compare treebanks? TIGER and TüBa-D/Z revisited

Proceedings of the Sixth International Workshop on Treebanks and 
\nLinguistic Theories.
\nEditors: Koenraad De Smedt, Jan Hajič and Sandra Kübler.
\nNEALT Proceedings Series, Vol. 1 (2007), 115-126.
\n© 2007 The editors and contributors.
\nPublished by
\nNorthern European Association for Language
\nTechnology (NEALT)
\nhttp://omilia.uio.no/nealt.
\nElectronically published at
\nTartu University Library (Estonia)
\nhttp://hdl.handle.net/10062/4476.