(August 12, 2015, 12:49 PM EDT) -- FRANKFORT, Ky. — A group of companies that operate glass manufacturing plants and have been sued by other companies that contend that the glass manufacturers have contaminated groundwater filed a brief on July 21 in Kentucky federal court, arguing that discovery in the case should proceed strictly on the issue of class certification, with merits discovery postponed until class status is determined (Modern Holdings LLC, et al. v. Corning Incorporated, et al., No. 13-405, E.D. Ky.)....