Ludwig Valentin Lorenz is the discoverer of the "Lorenz gauge"!
  The letter reminds the historical fact that the known "Lorenz gauge" (or "Lorenz condition/relation") is first mentioned in a written form and named after Ludwig Valentin Lorenz and not by/after Hendrik Antoon Lorentz. 
Bozhidar Z. Iliev (Institute for Nuclear Research and Nuclear Energy,   Bulgarian Academy of Sciences, Sofia, Bulgaria)