You can find it here:
A Common Written Greek Source for Mark AND Thomas. By John Horman. Studies in Christianity and Judaism 20. Waterloo, ON: Wilfrid Laurier University Press, 2011. Pp. viii + 256. Cloth, $85.00. – Watts – 2014 – Religious Studies Review – Wiley Online Library.
I can’t reproduce it yet, but… I found the concept fascinating but deeply flawed. Horman (an independent researcher, which is awesome) has a great theory, but in the end, it is a theory biased on the need to make Thomas more canonical than the other Gospels. I just don’t see it. One thing Horman does (and Francis Watson does) is to de-gnostic-fy Thomas, which is a welcomed feature.