Hungarian Mathematical Olympiad (1964 1997):

Kseniya Garaschuk, "Grade Five Competition from the Leningrad Mathematical Olympiad: 1979–1992 "
English | ISBN: 3030529452 | 2020 | 178 pages | PDF | 2 MB

A. Gardiner, "The Mathematical Olympiad Handbook: An Introduction to Problem Solving Based on the First 32 British Mathematical Olympiads 1965-1996"
English | 1997 | pages: 252 | ISBN: 0198501056 | PDF | 9,1 mb

Mathematical Olympiad In China (2011-2014): Problems And Solutions (Mathematical Olympiad Series) by Xiong Bin
English | 2018 | ISBN: 9813143746 | 368 Pages | PDF | 4 MB

Jiagu Xu, "Lecture Notes On Mathematical Olympiad Courses: For Senior Section - Volume 2"
English | ISBN: 9814368962 | 2012 | 296 pages | PDF | 22 MB

Jiagu Xu, "Lecture Notes on Mathematical Olympiad Courses: For Junior Section, Vol. 1"
2010 | ISBN-10: 9814293547 | 184 pages | PDF | 1 MB

Jiagu Xu, "Lecture Notes on Mathematical Olympiad Courses: For Junior Section Vol.2"
2010 | ISBN-10: 9814293555 | 192 pages | PDF | 1 MB

Xu Jiagu - Lecture Notes on Mathematical Olympiad Courses: For Junior Section (2 Volume Set)
Published: 2009-12-11 | ISBN: 9814293539 | PDF | 400 pages | 1.66 MB

The Colorado Mathematical Olympiad and Further Explorations: From the Mountains of Colorado to the Peaks of Mathematics By Alexander Soifer (auth.)
2011 | 408 Pages | ISBN: 0387754717 | PDF | 4 MB

Lecture notes on mathematical olympiad courses: For junior section, By Jiagu X.
2010 | 190 Pages | ISBN: 9814293555 | PDF | 1 MB

Lecture notes on mathematical olympiad courses: For junior section, By Jiagu X.
2010 | 183 Pages | ISBN: 9814293547 | PDF | 1 MB