Two other major coal-mining centers, each producing coking-grade bituminous coal, have been developed in Honan since the late 1950's. Hopi, in northernmost Honan, arose in 1957 on the site of a small, primitive operation in a deposit of lean coal, low in volatile content. A city was established in that year, and the mining complex was linked by a 12-mile rail spur with Tangyin, on the main Peking-Hankow line. 1972, Theodore Shabad, “The North China Plain”, in China's Changing Map, New York: Frederick A. Praeger, →LCCN, →OCLC, page 119: