A database of agricultural literature created by the National Agricultural Library of the USDA from 1970 to present.
Some MeSH headings to get you started when searching PubMed.
Epidemiologic Factors (contains Bias, Causality)
Epidemiologic Methods (contains Data Collection, Epidemiologic Research Design and Statistics as Topic)
Health Policy
Evaluation Studies as Topic (contains Quantitative Research)
Public Health Practice
Public Policy
Qualitative Research
Stakeholders = Consumer Participation