Texas House of Representatives approved legislation that would amend the state constitution to prevent local authorities from reducing public employees vested pension benefits. The measure passed Tuesday 137-0. Texas is one of only nine states that do not protect vested benefits, said Randy Stalnaker, president of the Texas Association of Public Employee Retirement Systems, Houston, and chairman of the $1.8 billion Dallas Employees Retirement Fund. The large statewide systems are not affected by the proposed amendment. If the Senate approves the measure, it must then be approved by voters in a referendum, under state law.