It is possible to follow a minor from another faculty or university and let it count towards the Elective Space in Bachelor 3. 

If you wish to do a minor offered at another faculty/university, you need the approval of the Examination Board. Requests can be submitted via Osiris Case in Osiris Student. For more information about the application procedure, please refer to the article How to apply for permission to follow a Bachelor elective course outside RSM? 

You should take into account that every university has its own minor system and its own requirements. It is your own responsibility to look into this. 

For further information about minors at the EUR, please refer you