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- Year: 2000
- Author: Стойчева Е. Генова Д. Платникова Р. Андонова Ц.
- Language: Bulgarian, German
- Year: 2000
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- Language: English, Greek
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- Language: English, Greek
- Year: 1998
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- Language: English, Русский
- Year: 1993
- Author: Dr. Özgür Savaç et al.
- Language: German, Turkish
- Year: 2010
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- Language: German, English
- Year: 1990
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- Language: Русский, English
- Year: 1994