You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Estonian_language

Context:
It should be noted that Estonian words and names quoted in international publications from Soviet sources are often back-transliterations from the Russian transliteration. Examples are the use of "ya" for "ä" (e.g. Pyarnu instead of Pärnu), "y" instead of "õ" (e.g., Pylva instead of Põlva) and "yu" instead of "ü" (e.g., Pyussi instead of Püssi). Even in the Encyclopædia Britannica one can find "ostrov Khiuma", where "ostrov" means "island" in Russian and "Khiuma" is back-transliteration from Russian instead of "Hiiumaa" (Hiiumaa > Хийума(а) > Khiuma).

Question:
What famous encyclopedia contains a Russian back-transliteration of Estonian?

Encyclopædia Britannica