# Tag Info

Having looked through a number of quantum mechanics papers from the era, it is pretty clear that, as @M.Farooq points out, what Dirac is using in the supposed paper-of-origin is just an italic $h$, which he redefines as Plancks' constant (who originally used the $h$) divided by $2\pi$. So, that is for 1926. In 1931, Dirac is still doing the same thing (see, ...