SN 2013fs and SN 2013fr: Exploring the circumstellar-material diversity in Type II supernovae

NSF [AST-1005313, AST-1515559, AST-1211916]; Discovery Communications; NASA's Astrophysics Data Analysis Program [NNX13AF35G]; PESSTO (the Public ESO Spectroscopic Survey for Transient Objects Survey) ESO programs [188.D-3003, 191.D-0935]; National Science Foundation [AST-1210599]; Gary & Cynthia Bengier; Richard & Rhoda Goldman Fund; Christopher R. Redlich Fund; TABASGO Foundation; Miller Institute for Basic Research in Science (U.C. Berkeley)