August 10 (SeeNews) - Croatia's Hrvatski Telekom (HT) [ZSE:HT-R-A] will hire an investment bank to lead further the process for the sale of its 17.41% stake and the 36.90% stake held by Zagrebacka Banka [ZSE:ZABA] in Optima Telekom [ZSE:OPTE-R-A], the competition authority AZTN has said.