Abu Yusuf Yaqub ibn Ishaq al-Sabbah Al-Kindi (801 - 873) worked with Al-Khawarizmi and the Banu Musa Brothers to translate Greek scientific manuscripts in the "House of Wisdom" in Baghdad. In addition, Al-Kindi wrote many manuscripts and books of his own. Topics for these manuscripts included:

• Indian numbers
• The harmony of numbers
• Lines and multiplication with numbers
• Relative quantities
• Numerical procedures and cancellation
• The theory of parallel lines (and in particular lines which are non-intersecting and non-parallel)

• http://www-gap.dcs.st-and.ac.uk/~history/Mathematicians/Al-Kindi.html