In the template for Referral for a Short Work Experience you are asking the project manager if he/she could provide a referral.
Dear <Name, Surname>,
In light of our recent short, but excellent cooperation, where I was engaged as a freelancer on one of your assignments, it would be great if you could provide me with a referral that I can further use.
If you are willing to do this, please follow the link [link to form] where you can fill in the form. Also, please inform me whether it would be okay to use your name along with the referral.
Thank you for your support.
Best regards,