1983, 1984, 1985, 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, and 2008. 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 Bulgaria compiled from sources dating from 1983 to 2008. Heat flow is a measure of heat loss acros... International Heat Flow Commission.