After sending at least 42 threatening letters to over 25 American Jewish sites, a Maryland man pleaded guilty on Monday to 17 counts of threatening communications and eight counts of obstructing the exercise of religious belief.Garrett Park resident Clift Seferlis faces a maximum penalty of 19 years in prison, three years supervised release, and a $5,650,000 fine for sending threatening letters and postcards to Jewish museums, community centers, schools, non-profits, a kosher delicatessen, and