Add recommendation to use DOIs in references.
Add recommendation to use DOIs in references.

WarrenWeckesser/scipy,perimosocordiae/scipy,vigna/scipy,Stefan-Endres/scipy,WarrenWeckesser/scipy,Stefan-Endres/scipy,ilayn/scipy,Stefan-Endres/scipy,scipy/scipy,perimosocordiae/scipy,rgommers/scipy,andyfaff/scipy,endolith/scipy,mdhaber/scipy,endolith/scipy,anntzer/scipy,rgommers/scipy,andyfaff/scipy,rgommers/scipy,andyfaff/scipy,ilayn/scipy,anntzer/scipy,mdhaber/scipy,perimosocordiae/scipy,endolith/scipy,vigna/scipy,mdhaber/scipy,ilayn/scipy,vigna/scipy,mdhaber/scipy,Stefan-Endres/scipy,anntzer/scipy,mdhaber/scipy,scipy/scipy,rgommers/scipy,andyfaff/scipy,andyfaff/scipy,ilayn/scipy,WarrenWeckesser/scipy,rgommers/scipy,anntzer/scipy,scipy/scipy,endolith/scipy,Stefan-Endres/scipy,WarrenWeckesser/scipy,scipy/scipy,anntzer/scipy,WarrenWeckesser/scipy,endolith/scipy,andyfaff/scipy,Stefan-Endres/scipy,ilayn/scipy,perimosocordiae/scipy,mdhaber/scipy,anntzer/scipy,perimosocordiae/scipy,vigna/scipy,WarrenWeckesser/scipy,ilayn/scipy,scipy/scipy,perimosocordiae/scipy,endolith/scipy,scipy/scipy,vigna/scipy