If there are multiple unrelated authors, Author Sort should be:
last_primary & first_secondary last_secondary, first_primary
Code:
Smith & William Jones, John
which displays on the Kindle as
John Smith & William Jones
If there are multiple related authors, Author Sort should be:
last_primary, first_primary & first_secondary
Code:
Smith, John & Nancy
which displays on the Kindle as
John & Nancy Smith
Remember to check
Preferences|Conversion|MOBI|Use author sort for author.
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