Encyclopedia Britannica
Encyclopedia Britannica: Seki Takakazu
Britannica Encyclopedia offers a brief summary of the life and accomplishments of Japanese mathematician Seki Takakazu.
Curated OER
University of St Andrews: Takakazu Seki Kowa
This site from the University of St. Andrews provides a biography of the Japanese mathematician Takakazu Seki Kowa, also known as "The Arithmetical Sage".