Someone wants to take photos I took for them over to a third party for publication. What are my rights?

[Mike1942f]

"A verbal contract is worth the paper it is written on."
In one sense, you have full copyright ownership. If you have possession of the RAW files that you took (which normally contain information about the camera used to take them, I believe) then you could make an expensive court case that they have to pay you for further use. If you gave them a complete set and that is what they want to hand over, then you lost a lot of control. If they are just asking you now for the RAW and you had given them edited files for the fan base, then you have more control and a legitimate right to say, "You wanted files for your Facebook, etc., and I provided those. If you want something more, I was not employed by you and I own the files, so I have little control over the Facebook files you have, although we did not discuss extended use at the time, but I do not have to provide you with further access to my files unless you are willing to pay for that right and I want a signed document stating what you are buying, so we both have it in writing."
As for credit, do you want the 3rd party to put on the publications "Photo by YourName", then you have to see what the contract, agreement, etc. says and try to get them to sign it. And enforce it with the publication.