sentences:  During the period from the 1970s to the 1980s, a comprehensive subset of subject headings for Chinese language materials was gradually established in the Library of Congress Classification System so that almost a full spectrum of ancient and contemporary Chinese topics can be widely covered.As a result of this, the Library of Congress Classification System eventually replaced the Harvard–Yenching Classification System for all Chinese language materials acquired after the 1970s in many American Libraries.Though the system has largely been phased out, the system is still being used in some libraries for Chinese language materials acquired prior to the Library of Congress update.