STOCKHOLM, Sweden - Birgit Nilsson, whose prodigious voice, unrivaled stamina and thrilling high notes made her the greatest Wagnerian soprano of the post-World War II era, has died. She was 87. A funeral was held Wednesday at a church in her native town of Vastra Karup in southern Sweden with only her closest relatives attending, said Fredrik Westerlund, the church's vicar. He did not know when Nilsson died or the cause of death. Born on a farm in Vastra Karup, Nilsson reigned supreme at opera houses around the world during her long career, which began with her debut in 1946...