[API-users] Clipping occurrence data to a country

I noticed that e.g. "&country=NL" limits occurrence data even within the specified country. That is, for that country, I get less occurrence data than without the "&country=NL" Is this caused by wrong data, by data with the wrong (or no) country identifier attached ? Anyway, I now seek another solution, which is to clip the occurrence data to the specified country on the map. However, how do I get map data tiles with country borders ? I use EPSG:3575. Regards, Adriaan van Os