What does SPARQL stand for?

Dear list,
please clarify. I really hate not being able to answer simple questions.
Here are the inconsistencies I found:

*S*PARQL *P*rotocol *a*nd *R*DF *Q*uery *L*anguage
from http://en.wikipedia.org/wiki/SPARQL
(No authorative reference for the acronym found though)

*S*imple *P*rotocol *a*nd *R*DF *Q*uery *L*anguage
from Jeffrey Pollock. Semantic Web for Dummies. John Wiley & Sons Inc., 
Chichester, West
Sussex, Hoboken, NJ, 2009.

*SPA*RQL *Q*uery *L*anguage for *R*DF
from http://www.w3.org/TR/rdf-sparql-query/

*S*PARQL *P*rotocol for *R*DF
from http://www.w3.org/TR/rdf-sparql-protocol/

What is the best and most recent document I should reference in an 
academic paper?
All the best,
Sebastian

-- 
Dipl. Inf. Sebastian Hellmann
Department of Computer Science, University of Leipzig
Projects: http://nlp2rdf.org , http://dbpedia.org
Homepage: http://bis.informatik.uni-leipzig.de/SebastianHellmann
Research Group: http://aksw.org