I'm out of touch with the latest UK PPL Air Law syllabus but I doubt it requires you to read DOC7300 in its entirety.
The document was signed in December 1944 to form the basis of International Civil Aviation Rules that countries could align with.
Often reference is made to where the origin of a piece of legislation has come from and I suspect this is what you are seeing in your article.
Stick to the syllabus given by your course provider unless you really want to delve deeply into the subject. In which case 'Good Luck'.
