Key to the classifications of the patent specifications of France, Germany, Austria, Netherlands, Norway, Denmark, Sweden, and Switzerland, in the library of the patent office
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Key to the classifications of the patent specifications of France, Germany, Austria, Netherlands, Norway, Denmark, Sweden, and Switzerland, in the library of the patent office
（Patent office library : subject lists, no. 1）
Printed for His Majesty's Stationery Office by Darling & Son , Patent Office, 1915
3rd ed