Gw mau tau , dari Moméntum. Jelasin dalam bahasa sunda

is the electromagnetic vector potential

the charged particle's invariant mass

Serway, Raymond; Jewett, John (2003). Physics for Scientists and Engineers (6 ed.). Brooks Cole. ISBN 0-534-40842-7

Stenger, Victor J. (2000). Timeless Reality: Symmetry, Simplicity, and Multiple Universes. Prometheus Books. Chpt. 12 in particular.

Tipler, Paul (1998). Physics for Scientists and Engineers: Vol. 1: Mechanics, Oscillations and Waves, Thermodynamics (4th ed.). W. H. Freeman. ISBN 1-57259-492-6

'H C Verma' 'Concepts of Physics, Part 1' 'Bharti Bhawan'

For numericals refer 'IE Irodov','Problems in General Physics'