Photos (1024×768 px) of Circaetus gallicus heptneri (© Askar Isabekov) and some information (En) on the traits of Short-toed Eagle population in Kazakstan. Also see the page dedicated to the nominal subspecies. The site has bilingual content now.
We would like to bring an article of Prof. Vladimir Galushin to your attention. Now he is a head of the Working Group on Raptors of Northern Eurasia and also he is a honorary member of the Russian Bird Conservation Union. The work is dedicated to the nesting of Short-toed Eagle in the Ryazan’ Region (Centre of European part of Russia) /map/:
• Галушин В.М., 1959 – Некоторые данные по гнездованию змееяда в Рязанской области [Some data on the Short-toed Eagle breeding in Ryazan' Region] // Орнитология. М.: Изд-во МГУ, Вып.2. 153-156. (Ru)
And one more text (Ru), that is an extract from his book:
• Галушин В.М., 1980 – Хищные птицы леса [Birds of Prey of Forest] // Лесная промышленность, 160 c.
…with two illustrations of V.A. Gorbatov.
We would like to invite you to visit the website of Igor Karyakin: Russian Birds of Prey Researchers Club. General and some local /map/ information on Short-toed Eagle can be found there:
• Игорь Карякин, 1998 – Змееяд – Пернатые хищники Уральского региона. Соколообразные (Falconiformes) и Совообразные (Strigiformes). Пермь: Центр полевых исследований Союза охраны животных Урала / Социально-экологический союз: 180-189 – 
(Ru).
• Г.П. Дементьев, 1951 – Змееяд (Circaetus gallicus) – Птицы Советского Союза, т.1. – М.: Сов. наука – (Ru).
(the source is a subsection of the site: Publications)
One more general description (Ru) (composed, in this case, by Igor Karyakin) is located in the subsection titled Articles on Species.