JEEVAN REDDY, J. - The petitioners are registered dealers under the Central Sales Tax Act and the Andhra Pradesh General Sales Tax Act dealing in cotton and cotton yarn. By G.O.Ms. No. 167 (Revenue) dated 9th February, 1971, issued under section 9(1) of the State Act, the State Government granted exemption in the case of sales of hank yarn from the levy of tax under the said Act with effect from 9th February, 1971. The petitioners say that on account of the said exemption, they were not charging or collecting the sales tax from their customers on the sales of the said commodity. However, it appears that the State Government issued another notification G.O.Ms. No. 437 (Revenue) dated 18th May, 1971, rescinding the said G.O.Ms. No. 167 with effect from 19th April, 1971. The said G.O. was, however, published in the Andhra Pradesh Gazette only on 1st July, 1971. The petitioners say that they knew of the said rescinding G.O. only in the second week of July when a copy of the same was communicated by the Andhra Pradesh Chambers of Commerce and Industry to its members. In the assessment for the relevant year, the petitioners claimed exemption on a turnover of Rs. 10,60,496.00 and