Kumar, R., Research Methodology: A Step-by-Step Guide for Beginners, SAGE Publications, New York, USA, 2010.
Kothari, C. R., Research Methodology: Methods and Techniques, New Age International Publishers, New Delhi, India, 2004.
Gomez, K. A., Gomez, A. A. Statistical procedures for agricultural research, John Wiley and Sons, New York, USA, 1984.
Steel, Robert G. D., Torrie, J. H., Principles and procedures of statistics: a biometrical approach, McGraw-Hill, New York, USA, 1980.
