@conference {PighinMoschitti:2009:CoNLL, title = {Efficient Linearization of Tree Kernel Functions}, booktitle = {CoNLL{\textquoteright}09: Thirteenth Conference on Computational Natural Language Learning}, year = {2009}, month = {06/2009}, address = {Boulder, CO, USA}, author = {Daniele Pighin and Alessandro Moschitti} }