Assignments, etc., not to be valid unless in writing and duly executed.

    ¹[68. Assignments, etc., not to be valid unless in writing and duly executed.--An assignment of a patent or of a share in a patent, a mortgage, licence or the creation of any other interest in a patent shall not be valid unless the same were in writing and the agreement between the parties concerned is reduced to the form of a document embodying all the terms and conditions governing their rights and obligations and duly executed.]