Complex sentence: A collection of his hymns was published shortly after his death, several of which have survived into the 21st century; one of these, "Holy, Holy, Holy", is a popular and widely known hymn for Trinity Sunday.
Split into simpler sentences: A collection of his hymns was published shortly after his death; several of those have survived into the 21st century. One of his hymns, "Holy, Holy, Holy", is a popular and widely known hymn for Trinity Sunday.