Goyette, I., Ricard, L., Bergeron, J., & Marticotte, F. (2010). e‐WOM Scale: word‐of‐mouth measurement scale for e‐services context. Canadian Journal of Administrative Sciences/Revue Canadienne des Sciences de l'Administration, 27(1), 5-23.
You can find the full paper at this link: http://goo.gl/GA0Iee
By the way, my dissertation was just about WOM:
Matos, C. A., & Rossi, C. A. V. (2008). Word-of-mouth communications in marketing: a meta-analytic review of the antecedents and moderators. Journal of the Academy of Marketing Science, 36(4), 578-596.
Goyette, I., Ricard, L., Bergeron, J., & Marticotte, F. (2010). e‐WOM Scale: word‐of‐mouth measurement scale for e‐services context. Canadian Journal of Administrative Sciences/Revue Canadienne des Sciences de l'Administration, 27(1), 5-23.
I also found: CHU, S. C.; KIM, Y. Determinants of consumer engagement in electronic word-of-mouth (e-WOM) in social networking sites. International Journal of Advertising, v. 30, n. 1, p. 47-75, 2011.
For "Positive word-of mouth intention" - here is a good source
Ren, Y., & Lam, D. (2014). An investigation into the link between service quality dimensionality and positive word-of-mouth intention in Mainland China. Journal of Marketing Communications, (ahead-of-print), 1-11.