Some adjective clauses take commas to set them of, and some don't. The noun that the clause modifies determines whether the clause will be a comma clause or a no-comma clause, instead of something in the clause itself. Proper nouns Maria Torres, who works at Xerox, was recently promoted. Golden Gate Park, which borders Ocean Beach, has a museum, a tea garden, and an arboretum. Telephone numbers, which have many important new uses, are becoming scarce.
Homeowners hate crabgrass, which spoils the appearance of law ns.
Japanese cars, which are very well built, have captured a large share of the American market. Nouns preceded by possessive words usually take comma clauses. My neighbor, who moved in a year ago, likes loud music. Johnson's theory of turbulence, which is not well accepted by economists, may prove itself right this year. No-comma clauses modify nouns that require further identification.