Planck's constant (plängks), fundamental constant of the quantum theory. It is represented by the letter h and has a value of 6.63 × 10-34 J-sec. The combination h/2π, denoted by h (called "h-bar" ), occurs frequently.
"Planck's constant." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. (March 19, 2018). http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/plancks-constant
"Planck's constant." The Columbia Encyclopedia, 6th ed.. . Retrieved March 19, 2018 from Encyclopedia.com: http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/plancks-constant