Tag 129 million copies of free textbooks

What a massive task!

To tag 129 million copies of free textbooks, I'll assume you're referring to digital copies, as physical copies would be impractical to tag individually. Here's a plan to achieve this:

Step 1: Categorization and Organization

Step 2: Automated Tagging

Step 3: Manual Tagging

Step 4: Quality Control and Maintenance

Step 5: Integration and Accessibility

Challenges and Considerations

By following these steps and addressing the challenges and considerations, it's possible to tag 129 million copies of free textbooks and make them more accessible and useful for learners.