Sixty-four, or one-third, of the world's countries have religious symbols on their national flags, according to a recent article by Pew Research.

Pew analyzed data from ConstituteProject.org, the CIA World Factbook and country-specific government websites to identify the countries around the world that display religious imagery on their national flags. Of these countries, 31 have Christian imagery, 21 have Islamic symbols, three have Hindu/Buddhist symbols, two have specific Buddhist imagery, one has Jewish imagery and six display symbolism from other traditions.

Commenters on the article raised two primary concerns: Where is Vatican City and what do Austria's horizontal stripes have to do with religion?

In response to the former, author Angelina Theodorou noted that the countries included in her analysis were based on those in Pew's Religious Restrictions report, which did not include the Vatican.

Regarding Austria's seemingly secular flag, Pew Communications Director Katherine Ritchey directed HuffPost Religion to the CIA World Factbook, which states that the country's flag makes reference to Duke Leopold V's blood-soaked white robe following a battle during the Third Crusade. Needless to say, the stories behind these religious flags aren't always pretty.