Merv Fowler (1999). Buddhism: Beliefs and Practices. Sussex Academic Press. hlm. 65. ISBN978-1-898723-66-0.[pranala nonaktif permanen], Quote: "For a vast majority of Buddhists in Theravadin countries, however, the order of monks is seen by lay Buddhists as a means of gaining the most merit in the hope of accumulating good karma for a better rebirth."
KN Jayatilleke (1998). Early Buddhist Theory of Knowledge. Motilal Banarsidass. hlm. 24 with footnote 2. ISBN978-81-208-0619-1., Quote: "What evidence is there for the existence of Indra unless someone has seen him? One stanza in a hymn says, 'One and another say, there is no Indra. Who hath beheld him? Whom then shall we honor?' - Rigveda 8.100.3, in Griffith: 8.89.3"
KN Jayatilleke (1998). Early Buddhist Theory of Knowledge. Motilal Banarsidass. hlm. 24, 27–28. ISBN978-81-208-0619-1. Quote: "Here for the first time there is an expression of doubt about the possibility of knowing certain things and a dim awareness that some sort of evidence was necessary before we can afford to make factual assertions. What evidence is there for the existence of Indra unless someone has seen him? (...)"
KN Jayatilleke (1998). Early Buddhist Theory of Knowledge. Motilal Banarsidass. hlm. 68, 374. ISBN978-81-208-0619-1., Quote: "We may conclude from the above that the rise of Buddhism is not far removed in time from, though it is prior to, the Maitri Upanishad".