[Ausubel 61] Ausubel, D. and Fitzgerald, D.: The role of discriminability in meaningful verbal learning and retention, Journal of Educational Psychology, Vol.52, pp.266-274 (1961).
[Cunninghan 93] Cunninghan, D.J., Duffy, T.M., and Knuth, R.A.: The Textbook of the Future, in McKnight, C., Dillon, A., and Richardson, J. (eds): HYPERTEXT A Psychological Perspective, Ellis HorwoodLimited, pp.19-49 (1993).
[Domel 94] Domel, P.: WebMap-A Graphical Hypertext Navigation Tool, Proc. of Second International WWW Conference (1994).
[Fischer 98] Fischer, G., and Scharff, E.: Learning Technologies in Support of Self-Directed Learning, Journal of Interactive Media in Education, 98 (4) (1998).