Effect of ovariohysterectomy at the time of tumor removal in dogs with benign mammary tumors and hyperplastic lesions: a randomized controlled clinical trial - Kristiansen, VM; Nodtvedt, A; Breen, AM; Langeland, M; Teige, J; Goldschmidt, M; Jonasdottir, TJ; Grotmol, T; Sorenmo, K (J Vet Intern Med, 2013)