added (here) this quote:

]]>In mathematical theories the question of notation, while not of primary importance, is yet worthy of careful consideration, since a good notation can be of great value in helping the development of a theory, by making it easy to write down those quantities or combinations of quantities that are important, and difficult or impossible to write down those that are unimportant.

added these references, and added their doi etc.:

Early speculations trying to model the electron by a relativistic membrane:

{#Dirac62} Paul Dirac,

*An Extensible Model of the Electron*, Proc. Roy. Soc. A268, (1962) 57-67 (jstor:2414316)Paul Dirac,

*The motion of an Extended Particle in the Gravitational Field*, in Relativistic Theories of Gravitation, Proceedings of a Conference held in Warsaw and Jablonna, July 1962, ed. L. Infeld, P. W. N. Publishers, 1964, Warsaw, 163-171; discussion 171-175 (spire:1623740)Paul Dirac,

*Particles of Finite Size in the Gravitational Field*, Proc. Roy. Soc. A270, (1962) 354-356 (doi:10.1098/rspa.1962.0228)