Bever GPS Workshops
 ...
http://www.bever.nl/agenda/gps
GPSopleiding.nl
GPSopleiding.nl
http://www.gpsopleiding.nl/
Navigatie Cursus
Excellent free navigation courses - online marine resources to teach you to navigate safely - this course is highly recommended - recognized sailing schools in greece.
http://www.sailingissues.com/navcourse0.html