Vermont State Retirement System, Montpelier, is reviewing proposals in its search for investment consultants for the $1.1 billion state teachers retirement system, $1 billion state employees retirement system, and the $170 million municipal employees retirement system. Each system may hire its own consultant, said Marie Duquette, director of investments. Contracts have expired for Callan, consultant for the teachers plan, and Wilshire, consultant for the state and municipal employee systems; both firms were invited to bid. The search is being conducted as a matter of policy, she said. A selection will be made June 15.