Publishing while changing institutions I'm submitting an mathematics article concerning research that was done entirely while I was an undergraduate at University A.  This August I will be a graduate student at University B.  The only funding I received came from NSF through a ten week program at University C at the very beginning of the project, after which I finished the research on my own while attending University A.  On the other hand, while University B has nothing to do with the publication, it is the most up to date institution as far as contact information goes.

Should I put University A or University B as my affiliation (or both)?
The standard solution for your question is to indicate your current address in a footnote:


  Alexander Gruber a,†, Another O. Tor a
  
  a University A, Department of Criminology, 221B Baker Street, London (UK)
  † Currently at University B, Logic Department, Whitehaven Mansions, Sandhurst Sq, London (UK)


If you didn't use any of the resources of University B, that is the way to go. Otherwise, University B should be listed as an affiliation.

The situation regarding your University C is less clear to me: if you were affiliated with them, you need to list them. If they only “handled” the money given out by NSF, then simply mention them in the funding or acknowledgments section:


  Acknowledgments
  A. G. is grateful to NSF program #132-1237 for funding, administered by University C.