In "Life lessons" http://www.theguardian.com/science/2005/apr/07/science.highereducation?fb_ref=desktop The Guardian (7 April 2005)
“It is easy to create an interstellar radio message which can be recognized as emanating unambiguously from intelligent beings. A modulated signal (‘beep,’ ‘beep-beep,’. . . ) comprising the numbers 1, 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, for example, consists exclusively of the first 12 prime numbers—that is, numbers that can be divided only by 1, or by themselves. A signal of this kind, based on a simple mathematical concept, could only have a biological origin.. . . But by far the most promising method is to send pictures.”
Smithsonian magazine, May 1978, pp. 43, 44. Quoted in Awake! magazine, 1978, 8/22.
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Carl Sagan 365
American astrophysicist, cosmologist, author and science ed… 1934–1996Related quotes

As expressed in "The Mathematical Philosophy of Giuseppe Peano" by Hubert C. Kennedy, in Philosophy of Science Vol. 30, No. 3 (July 1963)
Peano axioms

The Construction of the Wonderful Canon of Logarithms (1889)

Florian Cajori in: A History of Mathematical Notations http://books.google.co.in/books?id=_byqAAAAQBAJ&pg=PT961&dq=Notations&hl=en&sa=X&ei=Wz65U5WYDIKulAW1qIGYDA&ved=0CBwQ6AEwAA#v=onepage&q=Notation&f=false, Courier Dover Publications, 26 September 2013, p. 47.

“There are 2 rules in life:
Number 1- Never quit
Number2- Never forget rule number 1.”

Source: A Discourse of Combinations, Alterations, and Aliquot Parts (1685), Ch.II Of Alternations, or the different Change of Order, in any Number of Things proposed.

6. Acknowledge mistakes. 7. Make the offer of friendship more than once. 8. Express curiosity about what the other is like.
Source: Raising the Peaceable Kingdom (2005), Ch. 5

On losing to Tim Mayotte in the Ebel US Pro Indoor Championships, NY Times (February 9, 1987)