Treatise on a Very Narrow Aspect of Study

This page is the CodyCross answer for the clue below from Professions, Group 1538, Puzzle 3 (Technicians).

Question is: Treatise on a Very Narrow Aspect of Study

and the answer is: MONOGRAPH

Word Meaning:

MONOGRAPH — A scholarly book or a treatise on a single subject or a group of related subjects; especially, such a document that is written by one person.

Definitions from Wiktionary.