There are several journals and publications that provide valuable tips and resources for improving problem-solving skills in the UPSC Mathematics Optional subject. These publications are specifically designed to help candidates prepare for the mathematics paper of the UPSC exam and enhance their problem-solving abilities. Some of these journals and publications include:

1. Mathematics Today: Mathematics Today is a monthly journal that covers various mathematical topics and provides solutions to challenging problems. It is an excellent resource for UPSC aspirants looking to improve their problem-solving skills in mathematics.

2. Mathematics Spectrum: This publication focuses on mathematics and its applications. It provides in-depth coverage of different topics, including problem-solving techniques. Mathematics Spectrum is a helpful resource for UPSC candidates preparing for the mathematics paper.

3. Mathematics Magazine: Mathematics Magazine is a renowned publication that covers a wide range of mathematical topics. It includes articles, problem-solving tips, and techniques to enhance problem-solving abilities. This magazine can be a valuable resource for candidates preparing for the UPSC Mathematics Optional subject.

4. UPSC Mathematics Optional Guidebooks: There are several guidebooks available in the market that specifically cater to the UPSC Mathematics Optional subject. These guidebooks offer comprehensive coverage of the syllabus, along with problem-solving strategies and practice questions. They can be immensely helpful in improving problem-solving skills for the UPSC exam.

5. UPSC Mathematics Optional Previous Year Question Papers: Solving previous year question papers is an effective way to improve problem-solving skills. Candidates can analyze the patterns, types of questions, and develop a better understanding of the exam format. This practice allows them to enhance their problem-solving abilities and familiarize themselves with the UPSC Mathematics Optional subject.

In conclusion, several journals and publications provide tips and resources to improve problem-solving skills in the UPSC Mathematics Optional subject. Candidates can refer to these publications, solve practice questions, and analyze previous year question papers to enhance their problem-solving abilities and excel in the UPSC exam.