source("http://bioconductor.org/biocLite.R")
biocLite("org.Hs.eg.db")
library("org.Hs.eg.db")

# mapped_genes are all the genes that org.HS.egPMID covers (the HS refers to homosapien).  These genes are in Entrez format.
# entrez2Pmid is a list taking entrez gene ids to a vector of Pmids.

mapped_genes <- mappedkeys(org.Hs.egPMID)
entrez2Pmid  <- as.list(org.Hs.egPMID[mapped_genes])

# now if you have an entrez gene id you can look up the relevant papers by doing

entrez2Pmid[myEntrezGene]