This is the wrong list for you. Kloster Lage and Rieste is located in Osnabrück county, you should go to Hannover-List.

The name Gortemoller or all variation of this you can't find in Germany.
But the German phone directory (www.teleauskunft.de) shows in Rieste this address of a farmer:

Tangemann-Stickfort, Aloys Bauer phone (05493) 241
  49597 Rieste

There you can find also 3 Korte addresses.