Extended analysis of a pseudo-spectral approach to the vortex patch problem Mattias Bertolino www.diva-portal.org/smash/get/diva2:1221196/FULLTEXT01.pdf
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Of course and as usual, this is not a real question, it is here, only a reference added to my project, that RG doesnt permit to add otherwise (at the time), eg here on its "suggestions" etc.