The Bible, predictably, is at the top of the list. According to the Guinness Book of World Records, more than 5 billion copies of the Bible have been produced. Other religious writings on the list include the Quran, which has 800 million copies, and the Book of Mormon, which has 120 million. The total number of books published in English alone is about 150,000, so the Bible accounts for about 2% of all books published in that language. However, the Bible is by far the most popular book among English-language readers: it is estimated that there are about 75 million Christians in over 200 countries who read the Bible regularly. According to a study conducted by the Pew Research Center's Forum on Religion and Public Life, half or more of all Christian adults (depending on how "Christian" is defined) around the world have read the Bible. Other major religious texts that are widely read include the Qur'an (mostly by Muslims), the Bhagavad Gita (mostly by Hindus), and the Tao Te Ching (mostly by Chinese Buddhists). In terms of sales, the Bible remains the best-selling book in the world, followed by the Qur'an. It must be noted that estimates regarding the numbers of copies that have been sold vary significantly between sources. For example, Guiness Book of Records claims that 5 billion copies of the Bible have been produced, while other estimates range from 100 to 250 billion.