Fill in the Blanks (Reading & Writing)

The modern passport, now a routine travel —documentdocumenteddocumentarydocuments, has a surprisingly recent history. Before the twentieth century, many travellers crossed borders with little more than a letter of —introductionintroduceintroducingintroductory. It was only after the First World War that governments began —issuingissueissuedissues standardised booklets to control migration and verify —identityidentifyidenticalidentification.