Indexing content in IList property

Hi,

I'm having a IList<ContentReference> property on a page and want to indexing it's content.

Indexing content in a content area works just fine,

http://world.episerver.com/documentation/Items/Developers-Guide/EPiServer-Find/8/Integration/EPiServer-75/Indexing-content-in-a-content-area/

But it doesn't seems to be the way to indexing IList content. Any ideas anyone? 

Thank you!