Improved cosmological constraints from a joint analysis of the SDSS-II and SNLS supernova samples by Betoule, M, Kessler, R, Guy, J, Mosher, J, Hardin, D, Biswas, R, Astier, P, El-Hage, P, Konig, M, Kuhlmann, S, Marriner, J, Pain, R, Regnault, N, Balland, C, Bassett, B, Brown, P, Campbell, H, Carlberg, R, Cellier-Holzern, F, Cinabro, D, Conley, A, D'Andrea, C, DePoy, D, Doi, M, Ellis, R