1. We are deeply indebted to Prof. AULHORN and Prof. HARMS who provided research facilities for the first two parts of this study and assisted us with their advice.
2. GREVE, 1971; GREVE & WIJNANS, 1973.
3. BEDWELL, 1967; FANKHAUSER & GIGER, 1968; GOLDMANN, 1969.
4. POLYAK, 1941; DOWLING & BOYCOTT, 1967.
5. V. D. BRINK, 1965; V. D. BRINK & REYNTJES, 1966.