Understanding the Chess Openings by Sam Collins
https://web.archive.org/web/20140627031504/http://www.chesscafe.com/text/hansen76.pdf
http://www.gambitbooks.com/pdfs/Understanding_the_Chess_Openings.pdf
Understanding the Chess Openings by Sam Collins
https://web.archive.org/web/20140627031504/http://www.chesscafe.com/text/hansen76.pdf
http://www.gambitbooks.com/pdfs/Understanding_the_Chess_Openings.pdf
thanks