APA

Ludwig A., Gerhardt B. & Dale J. (1980). Materials and techniques for improving the engineering properties of sulfur. San Antonio, TX: Southwest Research Institute.

Chicago

Ludwig AC, Gerhardt BB and Dale JM. 1980. Materials and techniques for improving the engineering properties of sulfur. San Antonio, TX: Southwest Research Institute.

Harvard

Ludwig A., Gerhardt B. and Dale J. (1980). Materials and techniques for improving the engineering properties of sulfur. San Antonio, TX: Southwest Research Institute.

MLA

Ludwig AC, Gerhardt BB and Dale JM. Materials and techniques for improving the engineering properties of sulfur. San Antonio, TX: Southwest Research Institute. 1980.