A few words are differently spelled by different authorities.

There are seven of these authorities of the first rank, three English, Stormonth, the Imperial Dictionary, and the Oxford Dictionary; and four American, Webster's International, Worcester, the Century Dictionary, and the Standard Dictionary.

American printers may ordinarily disregard the English authorities.
Any one of the four American authorities may be safely followed.

In cases where two spellings are given in the dictionary consulted, take the first one.

Ordinarily a printing office adopts one of the great authorities as a standard and conforms the office style to it.