Perhaps you should try some spelling variations:
"Foundations of modern economics theories" » "Foundations of modern economic theories", "Foundations of modern economic theory", "Foundations of modern economicos teoria", "Foundations of modelo economico theories", "Foundations of modelos economicos theories"
"Foundations of poder economico series" » "Foundations of poder economica serie", "Foundations of poder economico spines", "Foundations of poder economico sociales", "Foundations of orden economico series"

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• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"Foundations of poder economico series\") OR (\"Foundations of modern economics theories\"))~".
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