Introduction:
Solving previous years' papers is an important part of exam preparation, especially for competitive exams like UPSC. It helps in familiarizing oneself with the exam pattern, types of questions asked, and the level of difficulty. However, the approach to solving these papers can vary based on individual preferences and study materials available.

Using Reference Books:
Using reference books can be beneficial while solving previous years' papers. These books often provide detailed explanations and solutions to the questions asked in the papers. Here are a few reasons why using reference books can be helpful:

1. Conceptual Clarity: Reference books often provide in-depth explanations of concepts, theories, and formulas related to various subjects. By referring to these books, you can strengthen your understanding of the topics and improve your problem-solving abilities.

2. Additional Practice: Reference books usually contain a wide range of practice questions, including those similar to the ones asked in previous years' papers. By solving these additional questions, you can further enhance your knowledge and develop a strong foundation in the subject.

3. Alternate Approaches: Reference books often present alternate methods and approaches to solve a particular problem. This can be beneficial as it allows you to explore different strategies and choose the one that suits you best. It also helps in improving your problem-solving skills by exposing you to various techniques.

Using Study Materials:
Study materials specifically designed for exam preparation can also be a useful resource while solving previous years' papers. Here's why:

1. Focused Content: Study materials are curated to cover the entire syllabus in a concise and organized manner. They provide relevant information and concepts required to solve the questions in the previous years' papers. This saves time and helps you stay focused on the exam-specific content.

2. Revision Assistance: Study materials often include summaries, key points, and mnemonics that aid in quick revision. While solving previous years' papers, you can refer to these materials to refresh your memory on important topics and concepts.

3. Exam-oriented Approach: Study materials are typically designed to align with the exam pattern and requirements. They provide practice questions and mock tests that closely resemble the actual exam. Solving these questions along with previous years' papers can give you a realistic understanding of the exam and help you improve your performance.

Conclusion:
In conclusion, both reference books and study materials can be valuable resources while solving previous years' papers. The choice between the two depends on personal preferences and the availability of study materials. It is advisable to use a combination of both, as they complement each other in providing a comprehensive understanding of the subjects and enhancing problem-solving abilities.