See text on the page: "Fortepan is an online photo archives. All of the images are licensed under Creative Commons CC-BY-SA-3.0 and can be freely used. If you wish to publish any of them, please give the credit in the following format: FOTO:FORTEPAN / name of donor."
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to remix – to adapt the work
Under the following conditions:
attribution – You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.
share alike – If you remix, transform, or build upon the material, you must distribute your contributions under the same or compatible license as the original.