00470nam a22001457a 4500 11776 11776 210108b ||||| |||| 00| 0 eng d 621.61 I81 2641 Indian Standard Institution Indian standard dimensions for mushroom ventilators with fixed head - welded type New Delhi Indian Standard Institution 1966 5 p. 1.00 Indian Standard BK 0 0 ddc 0 621_610000000000000_I81 0 22133 CL CL 1967-01-06 Indian Standard Institution 621.61 I81 03121 2021-01-08 BK