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            1Guidelines in the acquisition of permit for sand and gravel and other construction materialsBaskı/Yayın Bilgisi 1990Kitap
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            2
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            3
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            4Philippine Rock Industries, Incorporated grinding rock becomes a successful business ventureBaskı/Yayın Bilgisi 1968Kitap
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            5Practical operating procedures for progressive rehabilitation of sand and gravel sitesBaskı/Yayın Bilgisi 1966Kitap
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            6