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3. C. P. Lonsdale, M. L. Lutz: Locomotive traction motor armature bearing life study (Lubrication engineering, Vol. 53, No 8, Park Ridge, Illinois: STLE, 1997), pp.12-19.
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5. W. Zwierzycki: Oil, lubricants and greases for motoring and industry (Radom, Wydawnictwo i Zaklad Instytutu Techniologii Eksploatacji, 2001), p.498 (in Polish).