About Book:

          The printing of the eighth edition of the book has provided me with an opportunity to completely go through the text. Minor additions and improvements have been carried out wherever needed. All the figures have been redone on the computer to make it clear and sharp.

            I am really thankful to the management and the editorial team of  S,Chand &Company Pvt. Ltd., New Delhi for doing an excellent job in publishing the latest edition of the book.

            Pointing out of errors and misprints in the text will be highly obliged and thankfully acknowledged. Any suggestions for further improvement of the book will be highly appreciated.