Good point: I didn't think to also provide in the fluent collections a simple sort on the natural order of the items in the list. I will add it for sure in the next release.
The only (only) thing you could do at the moment is using the Collections.sort java method like in:
Collections.sort( with(pointOfSales).extract(on(POS.class).getCity()). ... )
Thanks for pointing this out.
Mario