dispensed with if the items are set in italics or quotes: The xs of the equation Dot the 'i's and cross the 't's In Latin, and continuing to the derivative forms in European languages as well as English, single-letter abbreviations had the plural being a doubling of the letter for note-taking. Most of these deal with writing and publishing. A few longer abbreviations use this as well. Conventions followed by publications and newspapers United States Publications based in the U.S. tend to follow the style guides of The Chicago Manual of Style and the Associated Press. The U.S. Government follows a style guide published by the U.S. Government Printing Office. The National Institute of Standards and Technology sets the style for abbreviations of units. United Kingdom Many British publications follow some of these guidelines in abbreviation: For the sake of convenience, many British publications, including the BBC and The Guardian, have completely done away with the use of full stops or periods in all abbreviations. These include: Social titles, e.g. Ms or Mr (though these would usually have not had full stops—see above) Capt, Prof, etc.; Two-letter abbreviations for countries ("US", not "U.S."); Abbreviations beyond three letters (full caps for all except initialisms); Words seldom abbreviated with lower case letters ("PR", instead of "p.r.", or "pr") Names ("FW de Klerk", "GB Whiteley", "Park JS"). A notable exception is The Economist which writes "Mr F. W. de Klerk". Scientific units (see Measurement below). Acronyms are often referred to with only the first letter of the abbreviation capitalized. For instance, the North Atlantic Treaty Organization can be abbreviated as "Nato" or "NATO", and Severe Acute Respiratory Syndrome as "Sars" or "SARS" (compare with "laser" which has made the full transition to an English word and is rarely capitalised at all). Initialisms are always written in capitals; for example the "British Broadcasting Corporation" is abbreviated to "BBC", never "Bbc". An initialism is also an acronym but is not pronounced as a word. When abbreviating scientific units, no space is added between the number and unit (100mph, 100m, 10cm, 10°C). (This is contrary to the SI standard; see below.) Miscellaneous and general rules A doubled letter appears in abbreviations of some Welsh names, as in Welsh the double "l" is a separate sound: "Ll. George" for (British prime minister) David Lloyd George. Some titles, such as "Reverend" and "Honourable", are spelt out when preceded