Books
ПУТЕШЕСТВІЕ ГОСУДАРЯ ИМПЕРАТОРА НИКОЛАЯ II НА ВОСТОКЪ (ВЪ 1890—1891) | Travel of Emperor Nikolai II to the East
by E. E. Ukhtomsky
Siam, Annam, and (indirectly) Cambodia in this recollection of Tsarevich Nikolai II's travel to Asia.
In Russian