An early line notation for chemical structures. The symbols used are the upper-case letters of the alphabet (A–Z), the numerals (0–9), with three other symbols: the ampersand (&), the hyphen (-), and the oblique stroke (/), and a blank space. Atomic symbols with one letter, such as B and F, are unchanged. Frequently occurring elements with more than one letter and functional groups are also assigned one letter; for example, G stands for chlorine, Q for hydroxyl, and Z for NH₂. The numerals indicate the number of carbon atoms in an unbranched internally saturated alkyl chain. For example, CH₃ is denoted 1 and CH₃CH₂ is denoted 2. To establish the notation of a compound the characters for the fragments are given in an established order. For example, the notation for C₂H₅OH is Q2. Rules for structures with branched chains and fused rings are also given. WLN provides a short and unambiguous notation, which is suitable for database searches. This notation was devised by William Wiswesser (1914–89) in 1949.