Interstellar extinction curve variations towards the inner Milky Way: a challenge to observational cosmology

Nataf, D. M. and Gonzalez, O. A. and Casagrande, L. and Zasowski, G. and Wegg, C. and Wolf, C. and Kunder, A. and Alonso-Garcia, J. and Minniti, D. and Rejkuba, M. and Saito, R. K. and Valenti, E. and Zoccali, M. and Poleski, R. and Pietrzynski, G. and Skowron, J. and Soszynski, I. and Szymanski, M.~K. and Udalski, A. and Ulaczyk, K. and Wyrzykowski, L.