The mean magnetic field modulus of Ap stars G. Mathys, S. Hubrig, J. D. Landstreet, T. Lanz and J. Manfroid Astron. Astrophys. Suppl. Ser., 123 2 (1997) 353-402 Published online: 15 June 1997 DOI: 10.1051/aas:1997103