GK> As I mentioned here earlier there is the German term
 GK> "Lehrbuch", which may come close to that. However, I cannot
 GK> remember a German word for an "advanced" book. Is there an
 GK> English term for that?

There aren't separate words for introductory textbook and advanced
textbook.  We generally use only the former, and refer to the latter as
either an undergrad text (used in the upper-level undergraduate courses) or
grad-level text (used in the graduate courses).

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