This is the convention used by essentially all physicists and originates in Dirac's bra-ket notation in quantum mechanics.
The Strangest Man: The Hidden Life of Paul Dirac, Quantum Genius is a 2009 biography of quantum physicist Paul Dirac written by British physicist and author, Graham Farmelo, and published by Faber and Faber.
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Einstein Wrote Back is a memoir by Canadian physicist John Moffat which documents his encounters with various other famous physicists, including Niels Bohr, Albert Einstein, Erwin Schrödinger, Fred Hoyle, Wolfgang Pauli, Paul Dirac, Abdus Salam, and J. Robert Oppenheimer, as well as his work at Imperial College London, Princeton University, CERN, and the University of Toronto.
New participants were Niels Bohr, Aage Bohr, Paul Dirac, Walter Heitler, Eugene Wigner and Gregor Wentzel; while Kramers, MacInnes, Nordsieck, Pauling and Van Vleck who were at the Shelter Island Conference were absent.
The Strangest Man, 2009 biography of quantum physicist Paul Dirac written by British physicist and author, Graham Farmelo