C. Economic and S. Center, Piauí 's Regional Accounts Review, 2010.

L. G. Aretio, Education for Today, 1994.

M. Moore and G. Kearsley, Distance education: an integrated view, Thomson Learning, 2007.

A. Brazilian, Distance Education Association, Census EAD.br ? Analytic Report of Distance Learning in Brazil, 2012.

A. S. Godoy, Qualitative Research: fundamental types. Enterprises Management Review, pp.20-29, 1995.

J. Hartley, Case studies inorganizational research