Knowles, M., E.F. Holton, and R.A. Swanson. (1998). The Adult Learner: The Definitive Classic in Adult Education and Human Resource Development, 5th edition. Houston: Gulf Publishing.
Merriam, S.B., editor. (2001). New Directions for Adult and Continuing Education. San Francisco: Jossey-Bass.
Merriam, S.B., and R.S. Cafarella. (1998). Learning in Adulthood: A Comprehensive Guide. San Francisco: Jossey-Bass.
Vella, J. (2002). Learning to Listen, Learning to Teach: The Power of Dialogue in Educating Adults. San Francisco: Jossey-Bass.