Changes

Summary

1. merged
2. misc tuning and modernization;
3. misc tuning and modernization;
4. clarified def vs. ref focus, e.g. for calculation vs. command refs;
5. entity markup for calculation;
6. tuned;
7. more markup for unstructured calculation;
8. tuned proofs -- avoid unstructured calculation;
9. tuned proofs -- avoid improper use of "this";