Who is Stavros Glavanis and Jan Eyken from The Tears of Autumn and what is their importance?

Stavros Glavanis and Jan Eyken

A Macedonian-Greek terrorist with credentials dating back to resistance against the Nazis and Greek communists, Glavanis honed his skills in the French Foreign Legion in Algeria and Asia. Paul Christopher hires him and French Foreign Legion comrade, the Flemish Jan Eyken, to kidnap and terrorize the U.S. Mafia boss Frankie Pigeon, in order to confirm Pigeon's involvement in the execution of accused Kennedy assassin Lee Harvey Oswald. Paul worries about Eycken being identifiable, because he lost both thumbs to Algerian terrorists years before, but Eycken wears rubber gloves. He resorts to water torture because it is his favorite technique. Both men are disappointed that Paul leaves Pigeon alive and tell him one day his humanity will cost him dearly.