30. For the purpose of recognising a candidate, within the realm of selection to employment in government services, under PSTM category, a candidate should have studied in Tamil as medium of instruction. Therefore, in order to avail the benefit of reservation earmarked under PSTM category, a candidate has to furnish a certificate to the effect that he or she studied in Tamil as medium of instruction. Such certificate will be issued by the Head of the Institution/Registrar or Principal of the College, as has been contemplated under G.O. (Ms) No.145, Personnel and Administrative Reforms Department dated 30.09.2010, in the prescribed format, certifying that he or she studied the course in Tamil by indicating the duration (academic year) during which the candidate pursued the course. It is this certificate which will form the basis for recognising a candidate for having studied in Tamil medium of instruction so as to enable him or her to get the benefit of reservation under PSTM category. It is needless to mention that merely because a candidate writes the academic examination or competitive examination in Tamil, it will not recognise such candidate to get the reservation under PSTM category. The requirement is that a Certificate issued by the Head of the Institution/ Registrar or Principal of the college, in the prescribed format, certifying that he was imparted with the course in Tamil as medium of instruction, has to be furnished, so as to enable a person to get the benefits of reservation under PSTM category. In the absence of such a certificate, a candidate cannot be regarded or recognised as a preferential candidate, who can avail the benefit of reservation under PSTM category. In other words, if such a certificate is not produced, he or she cannot be recognised as a candidate, who can be extended the benefit of reservation under PSTM category. Therefore, we hold that compliance of the requirements contemplated under G.O. (Ms) No.145