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Optical Levels, Automatic Optical Level Instruments | RS
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Stanley Telescopic Pole, 1-77-161 Extension Pole, For Use With Multiline And Optical Levels, Rotary...
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https://research.ibm.com/publications/effect-of-deep-levels-on-the-optical-and-electrical-properties-of-copper-doped-gaas-p-n-junctions
Effect of deep levels on the optical and electrical properties of copper-doped GaAs p-n junctions...
Effect of deep levels on the optical and electrical properties of copper-doped GaAs p-n junctions for Physical Review by T.N. Morgan et al.