Sorting through old letters

When my father died he left a lot of letters, which he had received during his lifetime. After he passed away my mother took care of those letters, and then when she died the letters ended up with me. It is a lot of work going through them all, deciding which ones should be donated to a museum and which one to keep in the family. My sister started the work when she visited (she lives in Norway) and now it's up to me to finish!