On the incidence of weak magnetic fields in DA white dwarfs J. D. Landstreet, S. Bagnulo, G. G. Valyavin, L. Fossati, S. Jordan, D. Monin and G. A. Wade A&A, 545 (2012) A30 Published online: 31 August 2012 DOI: 10.1051/0004-6361/201219829