As his country commemorates the 50th anniversary of the Soviet invasion that crushed an effort to ease the totalitarian grip of Communism known as the Prague Spring, the Czech Republic’s president is staying silent. Milos Zeman, an ardent supporter of Russian President Vladimir Putin, refused to mark Tuesday’s anniversary of the 1968 invasion of then Czechoslovakia. "I’m calling on you not to neglect your constitutional obligations,” Jiri Pospisil, head of the opposition party TOP 09 and a former justice minister, wrote in an open letter to Zeman. "Despite your pro-Russian sympathies, both you and I are citizens of one country...