APA
Helrich K. (., . (1990). Official methods of analysis of the association of official analytical chemists AOAC (vol-1): agricultural chemicals, contaminants, drugs. Wilson boulevard: Association of Official Analytical Chemist.
Chicago
Helrich Kenneth (ed.), . 1990. Official methods of analysis of the association of official analytical chemists AOAC (vol-1): agricultural chemicals, contaminants, drugs. Wilson boulevard: Association of Official Analytical Chemist.
Harvard
Helrich K. (., . (1990). Official methods of analysis of the association of official analytical chemists AOAC (vol-1): agricultural chemicals, contaminants, drugs. Wilson boulevard: Association of Official Analytical Chemist.
MLA
Helrich Kenneth (ed.), . Official methods of analysis of the association of official analytical chemists AOAC (vol-1): agricultural chemicals, contaminants, drugs. Wilson boulevard: Association of Official Analytical Chemist. 1990.