Original sentence: Its use is a historical artifact (written during the time when the amu scales were used), an error (possibly deriving from confusion about historical usage), or a correct reference to the historical scales that used it (see History).The atomic mass unit is also the name for two older units (both having the symbol amu) that are very similar to the modern atomic mass unit
Edited sentence: Its use is a historical artifact (written during the time when the amu scales were used), an error (possibly deriving from confusion about historical usage), or a correct reference to the historical scales that used it.The atomic mass unit is also the name for two older units (both having the symbol amu) that are very similar to the modern atomic mass unit (see History)