1. Validity in Survey Research;Belson,1986
2. A concordance correlation coefficient to evaluate reproducibility;Lin;Biometrics,1989
3. Farmers' estimations as a source of production data. Methodological guidelines for cereals in Africa;Murphy;World Bank Technical Paper 132,1991
4. Validity of the survey method of research;Spillman;US Dep. Agric. Prof. Pap. 529,1917
5. Introduction to information-based complexity;Traub,1988