Karen Pryor's Clicker Training basics. This site has lots of articles teaching about clicker
training, capture training and shaping behaviour.
A YouTube video of a vet's talk on why proper nail trimming
is so important for a dog's whole body health. Dr. Garrett is a practising vet, and a dog performance competitor. Also talks
about HOW to cut the nails and maintain them. The video is long (14 minutes) but has a lot of great information.
Peer-reviewed studies on Spay/ Neuter