This journal provides immediate access to some articles. Volume 29(9); September 1943 Bacteriology Strain Specificity and Production of Antibiotic Substances: II. Aspergillus Flavus-Oryzae Group PMCID: PMC1078613 Biochemistry Competition between Free and Combined Nitrogen in Nutrition of Azotobacter PMCID: PMC1078614 Mathematics Dynamical Trajectories in a Resisting Medium PMCID: PMC1078608 Dynamical Trajectories of the Curvature Type PMCID: PMC1078609 Union-Preserving Transformations of Differential-Elements PMCID: PMC1078610 A Formula for the Stream Function of Certain Flows PMCID: PMC1078611 Correction Correction to “On Certain Non-Linear Differential Equations of the Second Order” PMCID: PMC1078612 Corrects: On Certain Non-Linear Differential Equations of the Second Order. Proc Natl Acad Sci U S A. 1943 July; 29(7): 222–223. Journal Matter Original table of contents page Administrative content — journal masthead, notices, indexes, etc. | ||