Usability studies about B2B service pages?

I'm looking for research done on best practices when designing and writing content for B2B consulting service pages.

A B2B consulting firm could be management consulting firms, law firms or advertising agencies that have divided their offer into several services such as competitive audit, consumer research, etc.

I know that Norman Nielsen Group has made a report on B2B website usability in general but I looking specifically for studies about making service pages useful and compelling.