Supplementary and reference books are highly recommended for Class 11 Commerce students as they provide additional content, explanations, and practice questions that can enhance their understanding and knowledge of the subject matter. Here are some popular supplementary and reference books that are recommended for Class 11 Commerce:

1. "Accountancy - Financial Accounting Part 1 and Part 2" by NCERT:
- This book is the official textbook for Accountancy prescribed by the NCERT for Class 11 Commerce students.
- It covers all the necessary topics and concepts in a comprehensive manner.
- However, for additional practice and deeper understanding, students can refer to supplementary books.

2. "Business Studies - Business Studies Part 1 and Part 2" by NCERT:
- This book is the official textbook for Business Studies prescribed by the NCERT for Class 11 Commerce students.
- It provides a basic understanding of various business concepts and principles.
- To further enhance their knowledge, students can refer to supplementary books.

3. "Economics - Indian Economic Development" by NCERT:
- This book is the official textbook for Economics prescribed by the NCERT for Class 11 Commerce students.
- It covers topics related to the Indian economy, development, and policies.
- To gain a deeper understanding and explore more examples, students can refer to supplementary books.

4. "Statistics for Economics" by T.R. Jain and V.K. Ohri:
- This book provides a comprehensive coverage of statistical concepts and their application in economics.
- It includes numerous examples, exercises, and practice questions to strengthen the students' understanding.
- It is highly recommended for students who want to excel in economics and statistics.

5. "Fundamentals of Financial Management" by Prasanna Chandra:
- This book covers various aspects of financial management, including financial analysis, planning, and decision-making.
- It provides a detailed explanation of concepts and includes case studies to apply the knowledge in real-life scenarios.
- It is a valuable reference book for students pursuing commerce or aspiring to pursue a career in finance.

In conclusion, while the NCERT textbooks are the primary source of information for Class 11 Commerce students, supplementary and reference books can provide additional content, examples, and practice questions to deepen their understanding and improve their performance. The mentioned books cover various subjects and are highly recommended for students who want to excel in their commerce studies.