Since I am not familiar with these 12 factors, I searched Google under the key words "human strengths" to get these possible sources:
(Broken Link Removed)
There are other sites out there, and you might want to revise your key words.
In the future, you can find the information you desire more quickly, if you use appropriate key words to do your own search. Also see http://hanlib.sou.edu/searchtools/.
I hope this helps.