Create a crosswalk from USPC patent technology numbers to more aggregated categories.

This is build on Appendix 1 from:

Hall, Bronwyn H., Adam B. Jaffe and Manuel Trajtenberg (2001). The NBER patent citation data file: Lessons, insights and methodological tools. NBER Working Paper No. w8498. (link)

For example, the patent "Musical instrument support" (check out the inventor), has the primary USPC classification 84/327. This has the category 69, "Miscellaneous-Others".