Hybrids and crossing principles

[DavTom]

Hi,

Sorry if there is already a thread covering this topic, but I could not find it.

Does anyone know a website or published article, etc... in which it is clearly explained:
- what are the easy crossings that do produce a plant that will produce fertile seeds (I am not interested in the obvious ones like Phals with Phals)
- what are the less easy crossing that produce a plant that may or may not produce fertile seeds
- What are the more difficult crossing that may or may not work at all

Examples/pictures of crossings would be a plus. But I am much more interested to know what are the applicable principles as I found a lot of confusion on internet about tribes, sub-tribes, genera, not to mention alliances, etc...

For instance, I have read that Vanda with Phals is a non easy but doable cross.

Many thanks in advance.

Dav