1. DLE (Diccionario de la Lengua Española, Real Academia Española, RAE) : http://dle.rae.es/
2. OED (Oxford English Dictionary, OUP) : http://www.oed.com/
3. Information source and evidentiality: What can we conclude?;Aikhenvald;Rivista di Linguistica,2007
4. The grammar of knowledge: a cross-linguistic view of evidentials and the expression of information source