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²⁰C has been observed in the fragmentation of 213 MeV/nucleon ⁴⁸Ca by Be: it is particle stable (ST81L). Assuming the mass excess of ²⁰C to be 37.3 MeV [see (78AJ03)], ²⁰C is then stable with respect to ¹⁹ + n and ¹⁸C + 2n by 3.2 and 3.75 MeV, respectively [see ¹⁸C and ¹⁹C]. See also (78AJ03) and (NA78E, KI81C; theor.).