Pollard Rachel E, Marks Stanley L, Leonard Rebecca, Belafsky Peter C
Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis, CA 95616, USA.
Vet Radiol Ultrasound. 2007 May-Jun;48(3):221-6. doi: 10.1111/j.1740-8261.2007.00232.x.