Businesses involved in publishing periodicals produce publications issued at regular intervals, such as magazines, journals, newsletters and specialist or trade titles. They may focus on a particular subject, profession, industry or readership, or provide general-interest content. Periodicals can be published in print, online or in both formats, with issues released weekly, monthly, quarterly or on another schedule. Typical services include planning editorial content, commissioning articles and photography, editing and proofreading, checking facts, and managing layout and design. Publishers may also arrange printing, digital production and distribution, manage subscriptions and provide content to libraries or other organisations. Advertising sales, sponsorship and partnerships can form part of the business, alongside income from subscriptions or individual issue sales.