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5. It should be noted that the shape of the anomaly between 1.55 and 1.60 K depends on the previous history of the sample. It is generally sharp as in Fig. 2 for freshly prepared samples, but tends to be smoother after a few hours of measurements without a new heating/cooling cycle. The grain structure of the polycrystalline solid, the 3He segregation at grain boundaries as well as possible impurities, may play some role in this effect.