History of Tae Kwon Do: Yulgok: Concise biography of this Korean thinker.
Ojukheon Municipal Museum: Place where Yulgok and his mother, Shin Saimdang, lived. Information on buildings, exhibits, and history.
Yul-Gok: Illustrated biography.
Yulgok Yi I (1536-1584): Bibliography of primary and secondary sources in various languages.