リチャード・バルガ
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Niethammer, W., & Varga, R. S. (1983). The analysis of k {\displaystyle k} -step iterative methods for linear systems from summability theory. en:Numerische Mathematik, 41(2), 177-206.
Eiermann, M., Niethammer, W., & Varga, R. S. (1985). A study of semiiterative methods for nonsymmetric systems of linear equations. en:Numerische Mathematik, 47(4), 505-533.