A bartender (also known as a barkeep, barman, barmaid, or a mixologist) is a person who formulates and serves alcoholic or soft drink beverages behind the bar, usually in a licensed establishment. Bartenders also usually maintain the supplies and inventory for the bar. A bartender can generally mix classic cocktails such as a Cosmopolitan, Manhattan, Old Fashioned, and Mojito. Bartenders are also usually responsible for confirming that customers meet the legal drinking age requirements before serving them alcoholic beverages. In certain countries, such as Canada, the United Kingdom, and Sweden, bartenders are legally required to refuse more alcohol to drunk customers. Historically, bartending was a profession with a low reputation. It was perceived through the lens of ethical issues and various legal constraints related to the serving of alcohol. The pioneers of bartending as a serious profession appeared in the 19th century. 'Professor' Jerry Thomas established the image of the bartender as a creative professional. Harry Johnson wrote a bartending manual and established the first bar management consulting agency. At the turn of the 20th century, slightly less than half the bartenders in London were women, such as Ada Coleman.