SOFIA (Bulgaria), September 20 (SeeNews) – The SOFIX-based exchange-traded fund (ETF) Expat Bulgaria [BUL:BGX] has increased its stake in Sirma Group Holding [BUL:SKK], Doverie United Holding [BUL:5DOV] and Industrial Holding Bulgaria [BUL:4ID] on September 19, after the companies were included in the SOFIX index as of September 18.