For reference, the sentence OP is referring to:
[...] consisting of 119 articles collected in 7 volumes, the first of which was published in 1972 and the last in 1992
In this case, it would be either the 119 articles or the 7 volumes mentioned beforehand. Logic and common sense would lead me to believe the author is referring to the 7 volumes, since it's the latest noun mentioned and makes more sense.
Here, "of which" is present to give the text some coherence and harmony, and I can't really think of a way to remove it without murdering the phrase.
You could try:
[...] consisting of 119 articles collected in 7 volumes. The first one was
published in 1972 and the last one in 1992.
But then again, I think the construction with "of which" gives more flow to the text.