@book{202290,
	author = {Zhivkov, Todor. and Balev, Milko.},
	title = {Science--a powerful productive force /},
	publisher = {Sofia Press,},
	year = {1986.},
	address = {Sofia :},
	note = {Selections translated from a 2 volume work with original title: Naukata--mogŭshta proizvoditelna sila.}
}