Learn English – Is it correct to say “…battle between x versus y”

First of all, "repeat" doesn't actually have a prefix. So, you aren't "peating" something again.
It's a word derived from French:

repeat
late 14c., from O.Fr. repeter "say or do again, get back, demand the return of" (13c.), from L. repetere "do or say again, attack again," from re- "again" + petere "go toward, seek, demand, attack" (see petition). Specific meaning "to take a course of education over again" is recorded from 1945, Amer.Eng. Related: Repeated; repeating. The noun is first recorded 1550s.

It has a prefix in Latin, but not in English.

As you can see, "repeat" can mean 'to do or say again', so "repeat" can be used to mean to 'resay'.

Interestingly, etymonline.com and dictionary.com both don't give records of 'resay'.

GrammarGirl did a whole post on this. She explains that there is a difference between between and among. She writes:

Here's the deal: you can use the word “between” when you are talking about distinct, individual items even if there are more than two of them. For example, you could say, "She chose between Harvard, Brown, and Yale" because the colleges are individual items.

She goes on to explain that in the following cases, you use the two slightly differently:

Relationships: The Chicago Manual of Style describes these as one-to-one relationships. Sometimes they are between two items, groups, or people, as in these sentences:

• Choose between Squiggly and Aardvark.
• Let's keep this between you and me.

Other times they can be between more than two items, groups, or people as in these sentences:

• The negotiations between the cheerleaders, the dance squad, and the flag team were going well despite the confetti incident.
• The differences between English, Chinese, and Arabic are significant.

On the other hand, you use “among” when you are talking about things that aren't distinct items or individuals; for example, if you were talking about colleges collectively you could say, "She chose among the Ivy League schools." If you are talking about a group of people, you also use “among”:

• Fear spread among the hostages.

• The scandal caused a division among the fans.

• Squiggly and Aardvark are among the residents featured in the newsletter.

Part of a Group: “Among” can also indicate that someone is part of a group or left out of a group, as in these examples:

• He was glad to find a friend among enemies.
• She felt like a stranger among friends.
• Sylvia was later found living among the natives.

From this, you were correct in your use of between. "Cook et. al." formed part of a distinct group of individuals, so you would use between.