This journal provides immediate access to some articles. Volume 30(5); May 15, 1944 Mathematics Permutable Periodic Transformations PMCID: PMC1078678 On the Arithmetic in a Group Ring PMCID: PMC1078679 Possible Numbers of Non-Invariant Operators of a Group PMCID: PMC1078680 Pathology and Bacteriology Strain Specificity and Production of Antibiotic Substances: III. Penicillium Notatum—Chrysogenum Group PMCID: PMC1078677 Physics The Biological Effects of X-Rays as a Function of Intensity PMCID: PMC1078681 | ||