I think the hard part of this study IS the variables. You could do a study of only stone pigs in Emporia, Kansas, and you would still have to contend with diet, water (bottled, tap, well), cage size, bedding, genetics, etc.
When I was expressing my frustrations to my local vet, who (until us) had never really dealt with stones in guinea pigs before, wondering what I was doing wrong, she said, "I don't think you're doing anything wrong. I am beginning to think that stones are extremely common. The difference is that you and Jim pay attention to your animals and recognize something is wrong."
- Knee Deep
You will not be able to post full text. Technically Sef shouldn't even pass around her copy via email. Unfortunately with papers copyright belongs to the publisher, not the author.
There's rules and regs on how many copies of articles can be made in a year, but rarely enforced (and usually there's another library that has the paper if the first one does not send it).