Although the Venn diagram helps to organize your thoughts, it does not address the issue of "how much?" It's still possible to retrieve too many useful items; even worse, you may retrieve too few.

For too much

• Add another concept, such as a specific application
• Limit by dates, such as the last 5 years
• Limit by language, such as English only
• Limit by document type, such as only journal articles

For too litle

• Remove one or more concepts from the Venn diagram lists
• Accept
  • all languages
  • all dates
  • all document types
  • all formats (print as well as online)

In fact, it's wise to begin a search by ignoring the dates, languages, etc. until you know what's available. If the important work is in Japanese, you may have to find translations or pick another topic.