Wolfram Research
Wolfram Math World: Sets
This page discusses sets and set theory in mathematics and probability, and it discusses the notation and properties of sets.
Purple Math
Purplemath: Set Notation
This resource explains concepts related to set notation and gives examples for each.
State Library of North Carolina
N Cpedia: Telephones
Telephones began to appear in North Carolina beginning in 1879, three years after Alexander Graham Bell's new invention had first been introduced at the Centennial Exposition in Philadelphia. On 10 March of that year, a telephone was...