Mathematics texts have been found that are quite ancient. Babylonian texts from 1800 B.C. and Egyptian texts from 2000-1800 B.C. have been found. These texts have information about the Pythagorean theorum, a widespread mathematical concept. Greeks refined mathematics with deductive reasoning and using proofs. Chinese math included a place value system and Hindu-Arabic mathematicians in the first century A.D. invented a numeral system that is still in use today. Mathematics has evolved over time and continues to do so as concepts are continually expanded upon.