You're absolutely right! Starting with existing research is a fantastic way to delve deeper into your MPhil topic. Here are some additional tips to refine your search and find relevant academic resources:

Refining Keywords:

• Specificity: Consider adding specific keywords related to your research focus. For example, instead of just "efficiency," you could use "cost-benefit analysis" or "transaction costs."
• Synonyms: Include synonyms or related terms to capture a broader range of research. For example, instead of just "intermediaries," you could also use "Beparis" or "Aratdars."
• Boolean Operators: Utilize Boolean operators like "AND," "OR," and "NOT" to refine your search further.

Search Strategies:

• Databases: JSTOR and Google Scholar are excellent starting points. Consider exploring other academic databases like ScienceDirect, WorldCat: https://www.worldcat.org/, or specific databases relevant to agriculture or economics.
• Advanced Search Options: Most academic databases offer advanced search options. Utilize these features to filter by publication date, author affiliation, or specific journals within your field.
• Citation Trails: Once you find a relevant article, explore its cited references and the articles that cite it. This can lead you to other valuable research papers on the topic.

Additional Resources:

• Institutional Repositories: Many universities maintain online repositories containing research publications by their faculty and students. Search repositories of universities in Bangladesh or other institutions focused on South Asian agriculture and development.
• Government Reports: Websites of government agencies like the Bangladesh Bureau of Statistics (BBS) or the Department of Agriculture Marketing (DoAM) might contain reports on vegetable marketing systems.

Example Searches:

• (Vegetable marketing system OR agricultural marketing system) AND Dhaka AND Bangladesh AND (efficiency OR sustainability OR price fluctuations)
• Cost-benefit analysis of vegetable marketing systems in South Asia
• Role of Beparis in Dhaka's vegetable supply chain

By combining these strategies and utilizing the keywords you mentioned, you'll be well on your way to finding a wealth of existing research to support your MPhil project.

Remember, effectively utilizing academic resources is a skill that takes practice. Don't hesitate to experiment with different search terms and databases to refine your research and find the most relevant sources for your MPhil investigation.