Use of a hyphen

Hi,

What is the correct way to use the prefix "re" with words that start with a vowel? Examples include:
realign or re-align
readjust or re-adjust
reemphasize or re-emphasize

I cannot find a rule that addresses this. Various sources use either one or the other method.

Oxford Dictionary of Current English
"re-" is normally used to distinguish a compound from a more familiar word[/quote], like this,

Familiar word: align
Compound: re-align

Familiar word: adjust
Compound: re-adjust

Familiar word: emphasize
Compound: re-emphasize

All the best,