00270nam a2200109 a 450000500170000008200130001710000150003024500340004526000450007930000230012463000130014720251202164319.0  a410bROG  aRoger Lass  aOn explaining language change  aLondonbCambridge University Pressc1980  a186 p.b22 cm.cHB  aLanguage