http://www.issia.cnr.it/ http://www.ba.iac.cnr.it/wp/ https://ntnucamp.sce.ntnu.edu.tw/ http://leda.elfak.ni.ac.rs/

Gaya APA

Covey, S, R. (1990). 7 Habits of Highly Effective People, The : Powerful Lessons in Personal Change (First Edition). New York, USA: Simon & Schuster.

Gaya MLA

Covey, Stephen, R.. "7 Habits of Highly Effective People, The : Powerful Lessons in Personal Change". First Edition New York, USA: Simon & Schuster, 1990. Academic.