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- Language: Spanish
- Year: 2004
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- Language: Spanish
- Year: 2011
- Author: Zoitl Alois
- Language: English
- Year: 2009
- Author: Saadat Hadi
- Language: English
- Year: 1993
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- Year: 1993
- Author: Kalaba Robert E., Bellman Richard
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- Year: 1964