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Fig. 6. For the degenerate cases one needs fake interactions such as δjkΔi. A cross with a circle is used to denote this term. The n-th order term such as δjkΔ(n) is represented by n crosses which are sticked together.
New Phys.: Sae Mulli 2022;72:537~543 https://doi.org/10.3938/NPSM.72.537
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