http://www.akcchf.org/news-events/news/health-implications-in-early.html
http://www.caninesports.com/uploads/1/5/3/1/15319800/spay_neuter_considerations_2013.pdf
http://www.naiaonline.org/pdfs/LongTermHealthEffectsOfSpayNeuterInDogs.pdf
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0102241
http://www.caninesports.com/uploads/1/5/3/1/15319800/spay_neuter_considerations_2013.pdf
http://www.naiaonline.org/pdfs/LongTermHealthEffectsOfSpayNeuterInDogs.pdf
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0102241