OVF format expectations

Is there a document anywhere that outlines the format that the OVFTool expects the OVF file to be in?

Such as: elements that ovfTool expects?

I have some OVF sources that are .9 and 1.0 compliant however, ovfTool does not 'like' them because the OVF is not written the exact same way as an ovfTool produced OVF of the same VM.  The VMware vmx setting, the resources subtypes are not there for example.  As these are VMware specific and optional.

Any guidance is greatly helpful.

Thanks!