In the caliphate of Othman it was discovered that there were serious differences between the readings of the Koran possessed by the Syrian troops and those of the Eastern soldiers, and Othman was urged to have a copy prepared which should be authoritative for the Moslem world. He appointed Zaid ibn Thabit and three members of the tribe of Koreish (Quraish) to do the work. Each of these made a copy of Abu Bekr's collection, carefully preserving Koreishite forms of words. How far the text was amended by the help of other copies is doubtful; in any case the mode of procedure was undoubtedly very conservative. The four similar manuscripts were sent, one each to Medina, Cufa (Kufa), Basra and Damascus, and an order was issued that all differing copies should be destroyed. In spite of the personal unpopularity of Othman this recension was adopted by the Moslem world and remains the only standard text. A few variant readings and differences of order of the _suras_ in the collections of Ubay ibn Ka`b and of Ibn Mas`ud were, however, known to later commentators. The only variants after the time of Othman were owing to different possible ways of pronouncing the consonantal text. These are usually of little importance for the meaning. As the text is now always vowelled, variations are found in the vowels of different copies, and the opinions of seven leading "readers" are regarded as worthy of respect by commentators (see Th. Nöldeke, _Geschichte des Qorans_, pp. 279 seq., Göttingen, 1860). Various characteristics enable one to establish with more or less certainty the relative chronological order of the _suras_ in the Koran, at any rate so far as to place them in the first or second Meccan period or that of Medina. The form of the sentences is a guide, for the earliest parts are usually written in the _saj`_ form (see ARABIA: _Literature_). The expressions used also help; thus the "O ye people" of the Meccan period is replaced in the Medina _suras_ by "O ye who believe." The oaths in the first Meccan period are longer, in the second shorter, and are absent in the Medinan. In the earliest period the style is more elevated and passionate. Occasionally the time of origin is determined by reference to historical events. In accordance with such principles of criticism two leading scholars, Nöldeke (_loc. cit._) and H. Grimme (in his _Mohammed Zweiter Teil_. _Einleitung in den Koran. System der koranischen Theologie_, Münster, 1895), have arranged the _suras_ as follows:-- _Order of Suras in Koran._ NÖLDEKE. _Mecca._ 1st to 5th yr. (a). 96. 74. 111. 106. 108. 104. 107. 102. 105. 92. 90. 94. 93. 97. 86. 91. 80. 68. 87. 95. 103. 85. 73. 101. 99. 82. 81. 53. 84. 100. 79. 77. 78. 88. 89. 75. 83. 69. 51. 52. 56. 70. 55. 112. 109. 113. 114. 1. 5th and 6th yr. (b). 54. 37. 71. 76. 44. 50. 20. 26. 15. 19. 38. 36. 43. 72. 67. 23. 21. 25. 17. 27. 18.