Question: The confucian academy, Dosan Seowan, located in the East Asian country bordered by China to the northwest and Russia to the northeast, was founded by two prominant Confucian scholars, one being known as Yi Yulgok. What was the "pen" name of the other founding scholar?
Sentence (from "Jeong Gu"): his nickname was Hangang(한강, 寒岡)·Hoiyunyain(회연야인, 檜淵野人), courtesy name was Dogah(도가, 道可), Gabo(가보, 可父).
Relevant evidence: No