If you find a recent publication (say work of 2015) that has some interesting sections credited to an author (original owner, say work of 1981) and you tried to access the original work/contents and you couldnt find it i.e maybe deleted or huge prize tag on it that you may not afford. How do you cite such a line of statement? Do you pretend to credit it to the authors of the recent publication? Does it constitute plagiarism to do so? Whats the way forward?