Indexes and GROUP BY

[John Kendall]

Not sure how indexes work with ORDER BY and GROUP BY.
What index should I create which will be used on

SELECT '' As ID, `Source Presidency` As Presidency, `Source Name` As Name,
MIN(`Source Year`) As `Start Date`, MAX(`Source Year`) As `End Date` FROM
burialdeathfull GROUP BY `Source Presidency`, `Source Name` ORDER BY `Source
Presidency`, `Start Date`

or even just

SELECT * FROM burialdeathfull GROUP BY `Source Presidency`, `Source Name`

Everything I try doesn't work.

Thanks

John