“It depends on the reason for your need of evidence. For example if you are applying for a job, the papers might be helpful as proof to an employer. If you are writing an article, you might begin by saying that these animals were neutered in such a such a place. If I received a grant and I need to measure success for the donor, I would have a chart that shows when the neutering took place, how many animals were neutered, and where it took place.”