Some nice articles:

1. "Thinking out of the box" by William G. McCallum, 2001
http://math.arizona.edu/~wmc/Research/NCTMCASArticle.pdf

2. "The social psychology of creativity: A componential conceptualization" by Teresa M. Amabile, 1983

http://psycnet.apa.org/journals/psp/45/2/357.pdf