How to cite an article from a magazine (no date, published quarterly) in MLA7?
The relevant citation is provided in the site itself.
 My Black Crime Problem, and Ours by John J. DiIulio, Jr. 
 City Journal, Spring 1996, pp. 14-28 

To cite in MLA7:

DiIulio, John J., Jr. “My Black Crime Problem, and Ours.” City Journal, Spring 1996: 14-28. Print.

Hope this answers your quesion.