Livio, Mario. Where and when did the symbols "-¨ ¨¨¨ +¨ originate. May 12, 2013. Huffpost. May 8, 2017 http://www.huffingtonpost.com/mario-livio/where-and-when-did-the-sy_b_2860100.html
"I JUST SUED THE SCHOOL SYSTEM!!!." Uploaded by Prince Ea, 26 september, 2017
https://www.youtube.com
Lavrov, Geri. Reference. 2017. LLC May 8, 2017
https://www.reference.com/math/invented-addition-9be974c2fa3a2fdf
Source: Boundless. "Basic Operations." Boundless Algebra Boundless, 3 Sep. 2016. Retrieved 9 May. 2017 from https://www.boundless.com/algebra/textbooks/boundless-algebra-textbook/numbers-and-operations-1/introduction-to-arithmetic-operations-9/basic-operations-60-11091/
"I JUST SUED THE SCHOOL SYSTEM!!!." Uploaded by Prince Ea, 26 september, 2017
https://www.youtube.com
Lavrov, Geri. Reference. 2017. LLC May 8, 2017
https://www.reference.com/math/invented-addition-9be974c2fa3a2fdf
Source: Boundless. "Basic Operations." Boundless Algebra Boundless, 3 Sep. 2016. Retrieved 9 May. 2017 from https://www.boundless.com/algebra/textbooks/boundless-algebra-textbook/numbers-and-operations-1/introduction-to-arithmetic-operations-9/basic-operations-60-11091/