Pornography is generally classified as either softcore or hardcore pornography. By Japanese law, the genitals of actors and actresses must be censored and up the mid-1990 so was the depiction of pubic hair. A few extremely flexible males can reach and stimulate their penis with their tongue or lips, and so perform autofellatio. Creampie scenes depart from heterosexual pornographic convention in favor of a depiction that more closely mimics sexual intercourse as performed in ordinary life; they have been called the counterimage of facials. This style of filming is in contrast to having a separate, momsex third-person camera crew filming all the action. It spawned numerous sequels, several of which won adult film awards. A somewhat controversial ejaculation control technique is to put pressure on the perineum, about halfway between the scrotum and the anus, just before ejaculating. Mammary intercourse is said by Alex Comfort to produce mutual orgasm in women with sensitive breasts , and it was one of the nine substitute exercises for penetrative sexual activities, as detailed in the Paradis Charnels of 1903. The anus has a relatively high concentration of nerve endings and can be an erogenous zone, and the receiver may receive pleasure from external anal stimulation. In human sexuality, a threesome is sexual activity that involves three people at the same time. Usually that person prefers to stage the wetting so that his/her legs become soaked with urine. A pearl necklace is a slang term referring to a sexual act in which a man ejaculates semen on or near the neck, chest, or breast of another person. Although pornography has usually focused on heterosexuality, hentai videos due to the prevalence of the heterosexual orientation, explicit gay material has a long history as well, which reaches back to Greek antiquity, if not to prehistory. Lesbian pornography made for women is usually made by women, and usually features women who identify as lesbian or bisexual. Watersports pornography features sexual activities involving urine, young gay porn such as golden showers.