A stress is put on the various methods of the relevant measurements rather than on the review of the measured values in comparison with the corresponding calculated values.
The methods of the measurements are classified into two : (i) optical methods and (ii) intensity methods. Among the first methods, the older methods were only briefly referred to, and more recently published methods, particularly those with interferome-ters, are explained in details. The second methods include many varieties of experiments, but relatively new studies are explained in details, with the stress on the use of the white radiation.
Finally, some studies which partially include computational procedures have been introduced.
