For material in Western languages, see the following resource in the general guide:
An introduction to English language material is
But most material is in non-Western languages (Korean and Japanese).
For an early English guide to that material see the
Extensive English notes on some 150 traditional Korean sources can be found in
An up-to-date guide on reference material in any Korea-related subject, with notes in English, is
A large scale index to books and articles on Korean historical subjects written in all languages covering the period from 1945 to 1995 is
The Korean encyclopedias to be consulted are
To help you with many aspects of Korean Studies there is the Korean to English