Complex sentence: He published his observations in 1755 ("Описание земли Камчатки "; English translation (1764) as"History of Kamtchatka"), although it should be noted that he drew extensively on the manuscripts of the deceased Georg Wilhelm Steller.
Split into simpler sentences: He published his observations in 1755 ("Описание земли Камчатки "; English translation (1764) as"History of Kamtchatka"). However, he drew extensively on the manuscripts of the deceased Georg Wilhelm Steller.