"Electrons." . . "Électrons." . . . . . "X-rays and electrons : an outline of recent X-ray theory"@en . "X-rays and electrons : an outline of recent X-ray theory" . . . . . . . "X-rays and Electrons. An outline of recent X-ray theory"@en . . . "X-rays and electrons : an outline of recent x-ray theory" . . . . . . . "X-rays and electrons an outline of recent X-ray theory"@en . . . . . . . . . . . . "X-rays and electrons; an outline of recent X-ray theory" . . "X rays and electrons"@en . "X-Rays and electrons : an outline of recent X-ray theory" . "X-Rays and electrons" . . "X-Rays and electrons"@en . . . "X-rays and electrons; an outline of recent x-ray theory"@en . "Rayons X." . . . . "X-Rays." . . "X-rays." . "Théorie quantique." . . "Quantum Theory." . .