1977, 1978, 1979, 1980, 1981, 1982, 1983, 1984, 1985, 1986, 1987, 1988, 1989, 1990, 1991, 1992, and 1993. International Heat Flow Commission, International Association of Seismology and Physics of the Earth's Interior, and Oklahoma State University. Department of Geography. Cartography Service. This point shapefile contains heat flow data for Zambia compiled from sources dating from 1977 to 1993. Heat flow is a measure of heat loss across ... International Heat Flow Commission.