Skritata ikonomika v Bălgarija (biznes), Dekemvri 2002 g (Centăr za izsledvane na demokracijata, 2003)
Vitosha Research conducted a research of the "hidden" economy among the business sector which encompasses 530 companies throughout the country. The fieldwork was carried out during the period November 25 - December 02, 2002. The survey method is personal standard interview