Authoritative sources for studying governance and polity for UPSC include the Indian Constitution, books by renowned authors like M. Laxmikanth, and government publications. Reports from institutions such as the Planning Commission and the National Commission for Women provide valuable insights into policy assessments and recommendations. Moreover, up-to-date materials from online platforms and coaching institutes can offer comprehensive coverage of the syllabus. Candidates should ensure their resources are credible and encompass diverse perspectives on governance to prepare effectively.