A Two-Tiered Approach to Assessing the Habitability of Exoplanets Schulze-Makuch, Dirk ; Méndez, Abel ; Fairén, Alberto G. ; von Paris, Philip ; Turse, Carol ; Boyer, Grayson ; Davila, Alfonso F. ; António, Marina Resendes De Sousa ; Catling, David ; Irwin, Louis N. Abstract Publication: Astrobiology Pub Date: December 2011 DOI: 10.1089/ast.2010.0592 Bibcode: 2011AsBio..11.1041S