When they assumes theirself muslim they need to should bleive in Quran and sunnah. Quran can prov the facts of caliph Abu bakr Usman and Umer so if any shiite cinsiders himself to become a muslim they shold need to beleive in Quran . We do concur with ShiaPen there http://dua-kumail97283.theobloggers.com/1923486/5-tips-about-ali-name-meaning-you-can-use-today