so. He was also an expert in the history and calculation of the numerical tables of mathematical functions, particularly logarithms. He devised new calculation methods for certain forms of tables. He developed his theory of telephone traffic over several years. His significant publications include: 1909 – "The Theory of Probabilities and Telephone Conversations", which proves that the Poisson distribution applies to random telephone traffic. 1917 – "Solution of some Problems in the Theory of Probabilities of Significance in Automatic Telephone Exchanges", which contains his classic formulae for call loss and waiting time. 1920 - "Telephone waiting times", which is Erlang's principal work on waiting times, assuming constant holding times. These and other notable papers were translated into English, French and German. His papers were prepared in a very brief style and can be difficult to understand without a background in the field. One Bell Telephone Laboratories researcher is said to have learned Danish to study them. The British Post Office accepted his formula as the basis for calculating circuit facilities. In 1946, the CCITT named the international unit of telephone traffic the "erlang". A statistical distribution and programming language listed below have also been named in his honour. See also Erlang – a unit of communication activity Erlang distribution – a statistical probability distribution Erlang programming language – developed by Ericsson for large industrial real-time systems Queueing theory Teletraffic engineering References 20th-century Danish mathematicians Danish engineers Electrical engineers Queueing theorists Danish statisticians Danish business theorists 1878 births 1929 deaths People from Ringkøbing-Skjern Municipality Danish civil engineers University of Copenhagen alumni