How to give credit to a person who researched and helped write an article without making him a co-author?

Question

The person did a lot of research, wrote parts of the article, etc. Credit to him will be given in the first footnote. What would be an eloquent way to say it?

Answer 1

What harm would it cause to say that anyway? Give the person the credit they are due. It sounds like they actually were a co-author albeit the 'junior' partner in a collaboration.