rules for ghosts

I know I've seen them referenced before online, but I can't seem to find the rules for ghosts in any of my supplements.

Where are the rules published?

Thanks,
eric

There are some rules in "The Broken Covenant of Calebais", which is choke-full of ghosts.

The Tremere section of True Lineages has a box called "Varieties of Ghost" (shouldn't that be Ghosts?) on pages 126-129.