The Hα Galaxy Survey - II. Extinction and [NII] corrections to Hα fluxes P. A. James, N. S. Shane, J. H. Knapen, J. Etherton and S. M. Percival A&A, 429 3 (2005) 851-867 Published online: 05 January 2005 DOI: 10.1051/0004-6361:20035892