Affiliation for a student's internship project Though related to this question on undegrad student affiliation, I am in a somewhat different situation…

I am an undergrad student at the Miskatonic University. For completion of their BSc, students at MU are required to perform a 6-week research project in a research lab, which I did with a professor at another institution: Unseen University. I loved it, extending my stay there for 3 more weeks into my summer break. Now, we will submit a paper with the results of that internship project, but I don't know what affiliation(s) to put.

The specifics are:


I am not paid by MU, and did not set foot there during my research project (not using the library, nothing)
I was not paid by the research institution (UU), either
Though I am keeping an eye on the research project, I did not do any significant work since my internship ended (vacations, then too busy with courses)


I think I should put UU as my affiliation, because I used their resources. But maybe UU being the affiliation of the main authors (grad student and professor on the project) is enough? And should I put MU as affiliation?
A paper that I have recently read may be a good reference (or example). As can be seen, one of the co-authors, Xuemei Liu is under Baidu, Inc. Shanghai. The research work was done when she (gender inferred from the name) was done during her internship at HP Lab.

She wrote the affiliation as Baidu, and used a star mark as the footnote indicating the work was carried out during her HP Lab internship period.



Update: Another more relevant example:

This paper here is exactly the case. The first author is a student under Shanghai Jiaotong University (student and thus, unpaid). The work of the paper was performed when he was an internship under Microsoft Research Asia. They adopted the same way: affiliation is still the university and a star footnote indicates the internship connection.