Straight quotation marks (or italicised straight quotation marks) are often used to approximate the prime and double prime, e.g. when signifying feet and inches or arcminutes and arcseconds. For instance, 5 feet and 6 inches is often written 5' 6"; and 40 degrees, 20 arcminutes, and 50 arcseconds is written 40° 20' 50". When available, however, primes should be used instead (e.g. 5′ 6″, and 40° 20′ 50″). Prime and double prime are not present in most code pages, including ASCII and Latin-1, but are present in Unicode, as characters and . The HTML character entity references are and , respectively.