From the U.S. Patent and Trademark Office:
More on the Cooperative Patent Classification (CPC) --- the classification system currently used in the U.S. and in the European Patent Office for advanced subject searching:
Other important websites for accessing patents and patent information:
Russ's Guide to Gazettes at the Hathi Trust helps to explain these next entries:
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 Generic License.