Spann D R, Sellon R K, Thrall D E, Bostian A E, Boston G T
Department of Companion Animal and Special Species, North Carolina State University, College of Veterinary Medicine, Raleigh 27606, USA.
Vet Radiol Ultrasound. 1998 Nov-Dec;39(6):532-5. doi: 10.1111/j.1740-8261.1998.tb01645.x.