returns NEPP (= the \*number\* of studies published by the authors of the primary studies supplied UNTIL the year when the
primary study was published), NEPPRecency (like NEPP, but limited to the number of years befor the publication as specified with the
recency argument), "Meaning of NEPP" and "Meaning of NEPPRecency" which explain what \*number\* exactly means (e.g., could be the mean
of the sum of each author's publication, or the sum of the maximum publications per year of the authors), and "primaryStudyList(full)",
which just returns the primaryStudyList supplied).