The Streamlined System is similar to the old 1952 BGN/PCGN System for the Romanization of Bulgarian, which had been official in the USA and the United Kingdom until 2013. The latter however transliterates the Cyrillic letters Х, Ь and Ъ as "KH", "’" (apostrophe) and "Ŭ", while the former uses "H", "Y" and "A" instead.