I did not find this article in the Database: Morgan, G. A., Harmon, R. J., & Maslin-Cole, C. A. (1990). Mastery motivation: Definition and
I checked our databases and we only have the Early Education and Development journal from 2005 to present available online. We do not have the older copies of this in print either. If you still need this article I would suggest making a request through Inter Library Loan. This can be done through your ILLiad account. If you need help setting up an account please let me know.
Hope this helps.