Ive had a scan about and cannot find the correct format to use in an spf record where you want to include: more than one domain.

For example, a nicely working example of an spf record with a single include domain is:-

Code:
IN TXT "v=spf1 a ptr include:blueyonder.co.uk -all"
If you wanted to include more than one domain, for instance multiple ISPs used by users, would it be:-

Code:
IN TXT "v=spf1 a ptr include:blueyonder.co.uk include: domain.com -all"
Or would you use a single include: and a separator eg comma or space.

eg:-

Code:
IN TXT "v=spf1 a ptr include:blueyonder.co.uk domain.com -all"
or

Code:
IN TXT "v=spf1 a ptr include:blueyonder.co.uk,domain.com -all"
Or is this even possible?

Any help appreciated.