context: An amendment to a law of September 1980 on air traffic, adopted in January 1981, prohibited the transport of radioactive substances by air without a special permit. Existing safety regulations were considerably extended and modified by the technical committees responsible for individual specialist areas. Regarding installations requiring supervision, the technical regulations for pressure containers (19 January 1982) and steam boilers (26 January 18 March and 8 June 1982) were extended and revised, with their most important provisions concerning the oil- and gas-firing of steam boilers. A Directive on connecting lines designed to carry dangerous fluids (11 June 1982) was issued, together with technical regulations on pressure gases (11 June and 9 July 1982) The existing technical regulations on flammable fluids were also modified and by means of new regulations and directives extended (19 April 1982). Other modifications were made to the technical regulations on high-pressure gas pipelines (22 June and 10 September 1982) and on installations where acetylene is present and calcium carbide is stored (30 September 1982), while new recommended levels for dangerous working substances were incorporated into the regulations governing these substances (10 May 1982).
question: How many times were the technical regulations on high-pressure gas pipelines modified?
answer: 2