I think the works of Organ et al  (1999), (2000) , also check those of Podsakoff et al ()', these authors when googled would give you useful links to solving your prooblem.

there are lot of papers on organisational citizenship behaviour that concentrate upon performing those roles for which you are not paid. employees do it due their pro-social behaviour. I have attached some of the papers

I have just published a measure I have developed in collective behavior of employees entitled: "Validating the organizational context measure for collective learning: a managerial action perspective". available on this site.I hope you find it useful.

Article Validating the Organizational Context Measure for Collective...