Subject librarian
Subject librarians (sometimes called specialist librarians or academic liaison librarians or bibliographers in US-English) are librarians who are in charge a particular academic topic in a library, like maths or linguistics. Subject librarians usually work in academic libraries and special libraries (like legal libraries or medical libraries), but are sometimes large non-academic libraries like a national or state library. In academic libraries, they work with the teachers who teach the topic they manage to make sure the library has good books for the topic, including books teachers tell the students to read.