I have logged in to the site via web browser, got the cookies.txt file using
browser extension <https://addons.mozilla.org/en-US/firefox/addon/cookies-txt/>
and placed this file into my project root folder. Also the user agent used by
the httrack had to be the same as my browser where i have logged in. Details
of the process using httrack GUI is at
<https://internetlifeforum.com/showthread.php?31114-Downloading-password-protected-site-using-httrack-website-copier>