The passage discusses several aspects of a "Dictionary" of chemical compounds, highlighting both its strengths and limitations. It notes that while the dictionary avoids duplication through cross-references, some entries, particularly those related to sulphur drugs and derivatives of heterocyclic amines, have discrepancies. The dictionary also includes many organic compounds of natural origin, but some notable ones like asarinin, stevioside, and dihydronorguaric acid are missing. Despite these issues, the reviewer, B. A. Ellis, emphasizes that the dictionary remains a valuable resource for information on compounds, except for newly described ones. The second part of the passage reviews two books on linear operators: "Measure and Integral, Banach and Hilbert Space. Linear Integral Equations" by Prof. Adriaan Cornelis Zaanen and "Spectral Theory and Some Other Applications" by Dr. Richard G. Cooke. Prof. Zaanen's book covers topics related to the classical theory of linear integral equations, including Lebesgue integration, $L_{p}$ spaces, Banach and Hilbert spaces, and the theory of bounded linear operators. Dr. Cooke's book focuses on spectral theory for self-adjoint linear operators in Hilbert space, with detailed proofs and applications in quantum mechanics. Both books are comprehensive references, but they cater to different audiences and have distinct focuses.The passage discusses several aspects of a "Dictionary" of chemical compounds, highlighting both its strengths and limitations. It notes that while the dictionary avoids duplication through cross-references, some entries, particularly those related to sulphur drugs and derivatives of heterocyclic amines, have discrepancies. The dictionary also includes many organic compounds of natural origin, but some notable ones like asarinin, stevioside, and dihydronorguaric acid are missing. Despite these issues, the reviewer, B. A. Ellis, emphasizes that the dictionary remains a valuable resource for information on compounds, except for newly described ones. The second part of the passage reviews two books on linear operators: "Measure and Integral, Banach and Hilbert Space. Linear Integral Equations" by Prof. Adriaan Cornelis Zaanen and "Spectral Theory and Some Other Applications" by Dr. Richard G. Cooke. Prof. Zaanen's book covers topics related to the classical theory of linear integral equations, including Lebesgue integration, $L_{p}$ spaces, Banach and Hilbert spaces, and the theory of bounded linear operators. Dr. Cooke's book focuses on spectral theory for self-adjoint linear operators in Hilbert space, with detailed proofs and applications in quantum mechanics. Both books are comprehensive references, but they cater to different audiences and have distinct focuses.