1. Goodings (1965), Kenney (1964), Lafon and Lin (1966), Meyer and Young (1965), O'Keefe and Goddard (1969), Overhauser and de Graaf (1969), Painter and Ellis (1970b), Rudge (1969c).
2. Kunz (1969b).
3. Kunz et al. (1969), Mansikka and Bystrand (1966), Mansikka et al. (1967), Roessler and Walker (1967c, d).
4. Kunz (1968).
5. Kunz (1969a).