Dividesnaturallyintoseveralpartsaccordingtothelevelofthematerial,thebackgroundrequiredofthereader,andthestyleofpresentationwithrespecttodetailsofproofs.Forexample,thefirstpart,toChapter6,isundergraduateinlevel,thesecondpartrequiresabackgroundinGaloistheoryandthethirdsomecomplexanalysis,whilethelastparts,fromChapter12on,aremostlyatgraduatelevel.