div class=trans-pagebuttonPage 1button div class=trans-image amp-img class=trans-thumb alt=Page 1: Production of Positrons by β-Rays src=https:reader035fdocumentorgreader035viewer2022081213575067d51a28ab0f07ad5d67html5thumbnails1jpg width=142 height=106 layout=responsive amp-img divp© 1936 Nature Publishing Grouppdiv