P. Haase, J. Broekstra, A. Eberhart, and R. Volz. International Semantic Web Conference, volume 3298 of Lecture Notes in Computer Science, page 502-517. Springer, (2004)
K. Cheung, H. Frost, M. Marshall, E. Prud'hommeaux, M. Samwald, J. Zhao, and A. Paschke. BMC Bioinformatics, (2009)"We have explored a tool called "FeDeRate", which enables a global SPARQL query to be decomposed into subqueries against the remote databases offering either SPARQL or SQL query interfaces.".