Former President Jimmy Carter returned to the U.S. today saying that he's obtained agreements from both sides to release all prisoners of war in the Bosnian conflict. Meanwhile, in Bosnia, U.S. peacekeepers moved quickly with preparations to implement the ceasefire set to go into effect at noon Friday. U.N. officials expressed optimism about the results of the Carter visit, with a spokesman for the forces there saying that they believe "both sides are serious in their pursuit" of a pact ending the conflict. The U.N. plans to place troops along a 750-mile corridor in an effort to maintain the ceasefire. Yet, even as the plans progressed, fighting was reported near Bihac, where four people were wounded during shelling at the town of Cazin.