Table 1 Some operators used in PubMed

[ti]

The term is considered as a free text keyword and searched for in title

[ab]

The term is considered as a free text keyword and searched for in abstract

[mh]

The term, a MeSH descriptor, and all the terms it subsumes, are searched for in MeSH indexing

[majr]

The term, a MeSH descriptor, and all the terms it subsumes, are searched for in MeSH major indexing

[nm]

The term, a MeSH supplementary concept, is searched for in MeSH indexing

[tw]

The term is considered as a free text keyword and searched for in multiple fields of PubMed citation (title, abstract, MeSH indexing, other keywords etc.)