- Author: Felipe Portocarrero S., Universidad del Pacifico. Centro de Investigacion.
- Language: Spanish
- Year: 2002
- Author: Roberto Urrunaga, Universidad del Pacifico., Jose Luis Bonifaz
- Language: Spanish
- Year: 2008
- Author: Cesar Gala Yampasi, Universidad del Pacifico., Fernando Gonzalez Vigil
- Language: Spanish
- Year: 2008