The names are Sprewanen and Heveller  - why Sprevjane and Havolane in Wikipedia ???
The overwhelming majority of google search results and books show Sprewanen for a former  tribe in Berlin area.

 Sprevjane  400 appr

[http://www.google.com/search?hl=en&q;=sprewanen&btnG;=Google+Search
sprewanen Sprewanen over 1600]

[http://books.google.com/books?q=sprewanen&btnG;=Search+Books&as;_brr=0    16 books Sprewanen

[http://books.google.com/books?q=sprevjane&btnG;=Search+Books&as;_brr=0

sprevjane  3 books Sprevjane] 

The same goes for the related Heveller in the same Berlin area

[http://books.google.com/books?q=heveller&btnG;=Search+Books&as;_brr=0 Over 200 books: Heveller 

[Havolane http://books.google.com/books?q=havolane&btnG;=Search+Books&as;_brr=0 2 books: Havolane]

Why are the odd unknown names Sprevjane and Havolane pushed in wikipedia???