Owing to inadvertent errors, in the right column on page 2 of the paper, in the definition of ω, the 'y' has been dropped from the word 'energy'
In addition to this on pages 6–7, in the list of sections and subsections, the Roman numerals of the main section titles (Preliminaries; Neutrons and the fission process; Critical mass and efficiency; Detonation, pre-detonation, and fizzles; Conclusion) should read I—V, respectively. Also, the subsections should be numbered consecutively from 1 (Object) through 22 (Conclusion). These designations were correct in the proof, but were inadvertently altered during the processing of the final files.
On page 20, right column, fifth line following equation (73), part of an expression was dropped. This should read ' ... reached at .'
Finally on page 29, footnote 5: this should refer to reference [20], not [22].