Complex sentence: He has published several books in the Cornish language including a beginner's course in Cornish "Holyewgh an Lergh"- "Cornish This Way", which was first published in 2004 and is accompanied by two cassettes.
Split into simpler sentences: He has published several books in the Cornish language including a beginner's course in Cornish "Holyewgh an Lergh"- "Cornish This Way". Which was first published in 2004 and is accompanied by two cassettes.