Hα surface photometry of galaxies in the Virgo cluster I. Observations with the San Pedro Martir 2.1 m telescopeG. Gavazzi, A. Boselli, P. Pedotti, A. Gallazzi and L. CarrascoA&A, 386 1 (2002) 114-123DOI: https://doi.org/10.1051/0004-6361:20020214