Pooled regression and covariance analysis of SMSA selected services: earnings and firm size.
Hoppes has investigated the relationship between service earnings per capita and service structure, including the regional variation in service structure using a selected group of service sectors. -P.Shoebridge
Hoppes, R. Bradley. "Pooled Regression and Covariance Analysis of SMSA Selected Services: Earnings and Firm Size." Journal of Regional Analysis and Policy 15, no. 1100-2016-90051 (1985): 30-45.
Regional Science Perspectives