REFERENCES
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- Kilp , M. , Knauer , U. , Mikhalev , A. ( 2000 ). Monoids, Acts and Categories . Berlin : Walter de Gruyter
- Bulman-Fleming , S. ( 1992 ). Flat and strongly flat S -systems . II. Comm. Alg. 20 : 2553 – 2567 .
- #Communicated by D. Easdown.