Taco Bell could hold the secret formula for bringing customers back to fast food CNNYum Brands reports mixed results as Pizza Hut and KFC same-store sales fall CNBCSlower KFC and Pizza Hut Sales Weigh on Yum Brands The Wall Street JournalTaco Bell still ‘crown jewel’ for Yum even as boycotts, KFC weakness weigh ReutersYum Brands ties mixed Q2 to sales slip, Mideast tensions Yahoo Finance