NEW DELHI: Growth in the country's crucial infrastructure sector slowed to a four-month low in September but remained robust, led by a double digit expansion in the coal segment, data showed on Tuesday.The core sector, spanning coal, crude oil, natural gas, refinery products, fertilisers, steel, cement and electricity, rose 8.1% in September, slower than the 12.5% in the previous month and shade lower than the 8.3% recorded in September last year, data released by the commerce and industry ministry showed.Crude oil was the only laggard, which contracted 0.4%...