Amalia Bures won a hard-fought three-set match on opening day. By THE STAR STAFF With key results in the group stage, Puerto Rican tennis players began to make their mark in the international J30 Bayamón tournament -- part of the ITF World Tennis Tour Juniors -- during matches held earlier this week at the Honda Tennis Center. Puerto Rican players Bela Martínez Rivero and Amalia Bures secured important victories on Monday that placed them firmly in contention within their respective groups....