A chum at my club has asked if anyone knows of available literature on the civil and administrative practices of Greek colonies on the Med and Black Sea (his main interest is Thrace)? I have no idea! Thank you in advance
https://archive.org/details/cu31924028575060/page/n109/mode/2up by Rostovtzeff may have something. His Social and Economic History of the Hellenistic also has some iirc. Old, but doubtless still has something useful.
There is a little in Lund's 'Lysimachus, a study in Early Hellenistic Kingship'.
Depending exactly what he's after, he might find something useful in Greek cities on the western coast of the Black Sea: Orgame, Histria, Tomis, and Kallatis (https://dr.lib.iastate.edu/entities/publication/89231c8f-8ae4-4c71-a2c7-f12585e75238) and in Classical Olbia and the Scythian World (https://www.amazon.co.uk/Classical-Olbia-Scythian-World-Proceedings/dp/0197264042/).