1. Djang, A., 1980, Algorithmic equivalence in quadratic programming. Unpublished Ph.D thesis: Stanford University, California, 206 p.
2. Dorn, W. S., 1960, Duality in quadratic programming: Quart. Appl. Math., v. 18, p. 155?162.
3. Dubrule, O., 1983, Two methods with different objectives: splines and kriging: Math. Geol., v. 15, p. 245?257.
4. Dubrule, O. and Kostov, C., 1986, An interpolation method taking into account inequality constraints: Methodology: Math. Geol., v. 18, n. 1, p. 33?51.
5. Galli, A., Murillo, E., and Thomann, J., 1984, Dual kriging?its properties and its uses in direct contouring, Proceedings of NATO-ASI Geostatistics for Natural Resources Characterization, Lake Tahoe, California, 1983: D. Reidel, Dodrecht, Holland, p. 621?634.