1、Title：Customer retention, loyalty, and satisfaction in the German mobile cellular telecommunications market
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VCC-42H1S7N-4&_user=10&_coverDate=05%2F31%2F2001&_rdoc=1&_fmt=high&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=1187103337&_rerunOrigin=google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=5aefa130e286b5b8272d98758f94340d
Author：Torsten J. Gerpott, , a, Wolfgang Rams, b and Andreas Schindler, c

2、Title: The economics of number portability: switching costs and two-part tariffs
Author : Aoki, R. and Small, J.,
Working paper, University of Auckland, November 1999.