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First of all, I just wanted to say thank you for your work in making pictures available on Wikimedia Commons.
I would like to use one of your photos in a publication I am working on at the moment, and since it will be produced by a charity organization my royalties are not large (and would quickly be swallowed up if I had to pay for images).
My publisher, however, has requested that I confirm with you that you are willing to give me permission to use the following:
Are you fine with this? If so, could you please e-mail me at firstname.lastname@example.org
Once again, thanks for your work and I look forward to hearing back from you.
All the best,
Dr Aaron Chalmers