Your extra recommender should be someone who either supervised your work (paid or voluntary) or (second priority) cooperated/worked with you during an extracurricular or a professional activity.
Your extra recommender should shed light on achievements, characteristics or experiences that were not covered in the mandatory recommendations.
For example, good extra recommenders could be:
- A parliament member whom you voluntarily helped during his primary elections campaign.
- A CEO for whom you did some voluntary/paid research a couple years ago.
- A university professor that you worked for as a teaching or research assistant.
- Your boss from a workplace which was not covered in the mandatory recommendations.