Becker and Huselid (1997)
Becker, Brian E. and Mark A. Huselid. "Human Resources Strategies, Complementarities, and Firm Performance." Presentation to the Academy of Management Annual Meeting, 1997.
Surveys 533 U.S. corporations on their human resource practices, then regresses the findings against a variety of financial metrics as reported by Compustat. Finds that firms with "high performance" HR systems (as defined by the authors) had higher price/book ratios, even after adjusting for other factors such as beta, sales growth, and R&D intensity).
A subsequent working paper dated July 1998 expands on this work, and can be downloaded at: