• If it is to be effective as a tool of thought, a notation must allow convenient expression not only of notions arising directly from a problem, but also of those arising in subsequent analysis, generalization, and specialization.

    Kenneth E. Iverson: If it is to be effective as a tool of thought, a notation must allow convenient expression not only of notions arising directly from a problem, but also of those arising in subsequent analysis, generalization, and specialization.
    "Notation as a Tool of Thought". Cvommunications of the ACM, 23 (8), (pp. 444 - 465), August 1980.