So I was browsing the Mathematics Subject Classification and various other classification schemes related to it when I read from multiple sources that there are certain fields of study or research not well-represented in the MSC. For example, you can find little information on quantum algebra, theory of equations, and Lie theory (although topics on Lie groups are readily available in the MSC, I'm referring to subjects such as Lie sphere geometry). So, I was wondering if someone could provide with a list of fields not well-represented or listed in the MSC as I couldn't find articles on this forum or elsewhere related to this specific topic.
This would also help others who are looking for such topics as well in the future. Thanks!