Completed the following sentence: First incorporated as East Pakistan Stock Exchange Association Ltd on 28 April 1954 and started formal trading in 1956. ️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️ ️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️ <unk> <unk> <unk> <unk>
1971<unk><unk><unk><unk> ️<unk>️<unk>️<unk>️<unk>️ The formula for calculating DSE all share price index was changed according to IFC on 1 November 1993. <unk> <unk> <unk> <unk> <unk> <unk>