ANSWER: P. S. Krishnan 

P. S. Krishnan is a retired official of the Indian Administrative Service (IAS) and has been effectively working for the reason for the headway and strengthening of the denied social classifications of Indian culture, the Scheduled Castes, Scheduled Tribes, and Backward Classes, for over about seven decades including his 35-year profession in the IAS.

He has been Secretary, Ministry of Welfare, Government of India; Member, National Commission for Scheduled Castes and Scheduled Tribes; Member-Secretary, National Commission for Backward Classes; and Chairman/Member of various Steering Committees and Working Groups of India's Planning Commission.  

He has been Honorary Advisor to the central government and certain State governments in issues identifying with the impeded social classes and aides numerous social associations and activists. He has authored books, papers, and articles widely.