Reference books and other tertiary resources are often overlooked sources of scholarly knowledge. If you want a great definition of a theory that goes beyond wikipedia, I highly recommend these titles held by UVic Libraries.
International Encyclopedia of Social and Behavioral Sciences [electronic resource] by 
Schooling and Society by 
A Dictionary of Education [electronic resource] by 
World Education Encyclopedia [electronic resource] by 
History of Education [electronic resource] by 
A Social History of Knowledge II by 
Encyclopedia of Social History [electronic resource] by Encyclopedia of Gender and Society [electronic resource] by 
The Encyclopedia of British Columbia by 
Handbook of Research on the Education of Young Children by 
Handbook of Critical Race Theory in Education by 
The Handbook of Institutional Research [electronic resource] by 
International Encyclopedia of Adolescence [electronic resource] by 
Handbook of Families and Aging by The Canada year book [electronic resource]
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