Hierarchy/Derived subclasses
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uspto searches
Patent Apps in 91/304Granted Patents in 91/304
Use the links above or do an advanced search in ppubs for:
(91/304.ccls. or 91/461.ccls. or 91/305.ccls. or 91/306.ccls. or 91/307.ccls. or 91/308.ccls. or 91/309.ccls. or 91/310.ccls. or 91/311.ccls. or 91/312.ccls. or 91/313.ccls. or 91/314.ccls.)
This will show what classes derive from the input. Ex: entering 43/42.24 shows the derived classes and the search that can be used to find patents or patent applications in those subclasses.