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certain fungi in relation to hydrogen ion concentration. Ann. Mo. Bot. Gard. 6: 
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14. SiJrensen, S. P. L. Enzymstudien II. Uber die Messung und die Bedeutung der 
Wasserstoffionenkonzentration bei enzymatischen Prozessen. Biochem. Zeit. 21 : 
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15. Martin, W. H. The relation of sulphur to soil acidity and to the control of potato 
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