@inproceedings{ Díaz_Valera,

author = { Ana Díaz Negrillo and Salvador Valera } ,

title = { Multi-level annotation with adjustable granularity in a corpus of learner English¿ },

booktitle = { CALICO 2008 },

year = { 2008 },

pages = { None - None },

location = { San Francisco, Estados Unidos },

}