5Kumar V, Petersen J A, Leone R P. How valuable is word of mouth? [ J ]. Harvard Business Review, 2007, 85 (10) : 139 - 144, 146,166.
6Schmitt P, Skiera B, Van den Buhe C. Referral programs and customer value [ J ]. Journal of Marketing, 2011,75 ( 1 ) : 46 -59.
7Silverman G. How to harness the awesome power of word of mouth[ J]. Direct Marketing, 1997, 60(7) : 32 -37.
8Ainsworth M D S, Bell S M. Attachment, exploration, and separation: Illustrated by the behavior of one-year-olds in a strange situation[ J]. Child Development, 1970, 41 ( 1 ) : 49 - 67.
9Fraley R C, Shaver P R. Adult romantic attachment: Theoretical developments, emerging controversies, and unansweredquestions[J]. Review of General Psychology, 2000, 4(2) : 132 -154.
10Hazan C, Shaver P R. Romantic love conceptualized as an attachment process [ J ]. Journal of Personality and Social Psy- chology, 1987, 52(3):511-524.
