http://reply.papertrans.cn/3/244/24303/24303-11.png
http://reply.papertrans.cn/3/244/24303/24303-12.png
Submitted on: 30 May 2000.
Revised on: 15 June 2000.
Accepted on: 30 June 2000.
Perspectiva Educacional---EDICIONES UNIV VALPARAISO
Submitted on: 01 November 2017.
Revised on: 09 November 2017.
Accepted on: 27 November 2017.
Perspectiva Educacional---EDICIONES UNIV VALPARAISO
Submitted on: 09 November 2008.
Revised on: 19 December 2008.
Accepted on: 31 December 2008.
NULL
http://reply.papertrans.cn/3/244/24303/24303-16.png
http://reply.papertrans.cn/3/244/24303/24303-17.png
Submitted on: 08 September 2008.
Revised on: 25 September 2008.
Accepted on: 21 October 2008.
NULL
Submitted on: 21 August 2000.
Revised on: 02 September 2000.
Accepted on: 08 September 2000.
Perspectiva Educacional---EDICIONES UNIV VALPARAISO
Submitted on: 22 April 2012.
Revised on: 17 May 2012.
Accepted on: 04 June 2012.
NULL