BELGRADE, Yugoslavia (April 11)—The World Bank is investing $20 million in Tigar A.D., the Serbian tire and rubber goods joint venture of Groupe Michelin and Tigar. The investment through the bank's private sector arm, International Financial Corp., will lead to the firm being reformed as Tigar M.H., according to Serbia's ministry of economy and privatization. Tigar M.H. will be 65-percent controlled by Tigar, 25-percent by Michelin and 10 percent by the IFC, whose expenditure includes a $16 million loan prior to the new firm's incorporation on Oct. 1. The bank agency will provide another $4 million as a direct equity investment in Tigar M.H., the Serb ministry said.