https://www.nlm.nih.gov/virtualtour/pdf/PubMedFinal_revised_2.pdf
https://www.nlm.nih.gov/oet/ed/pubmed/handouts/Tips_for_Using_PubMed_Factsheet_2021_English-508.pdf
https://www.providence.org/-/media/project/psjh/providence/socal/files/global/library/tips_for_using_pubmed_2022.pdf
https://grunigen.lib.uci.edu/sites/all/docs/gml/pubmed-basics.pdf
https://webmed.irkutsk.ru/doc/pdf/pubmed.pdf
https://grunigen.lib.uci.edu/sites/all/docs/gml/Ten+Ways+to+Improve+Your+PubMed+Search.pdf
https://www.ehu.eus/biofisica/juanma/mbb/pdf/pubmed_intro.pdf
https://www.cebm.net/wp-content/uploads/2015/12/PubMedStepbyStepFinal__ElectronicCigarettes_Sept2015.pdf