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With $|{\mathbf{k}}_i|=k$, elastic scattering into a propagating wavevector ${\mathbf{k}}_s$ samples Fourier transfer $\mathbf{\kappa }={\mathbf{k}}_s-{\mathbf{k}}_i$. These transfers satisfy the displayed shifted sphere relation. This reciprocal-space construction appears in crystallographic diffraction and the Fourier diffraction theorem.