1. Gardeñes E., Trepat A.: "Fundamentals of SIGLA, an Interval Computing System on the Completed Set of Intervals" Computing 24, Springer 1980.
2. Gardeñes E., Trepat A., Janer J.M.: "SIGLA-PL/I, development and applications" Interval Mathematics 1980, Ed. K. Nickel, Academic Press 1980.
3. Gardeñes E., Trepat A., Janer J.M.: "Approaches to simulation and to the linear problem in the SIGLA System" Freiburger Intervall-Berichte 81/8, Freiburg 1982.
4. Gardeñes E., Trepat A., Mielgo H.: "Present perspective of the SIGLA Interval System" Freiburger Intervall-Berichte 82/9, Freiburg 1982.
5. Gardeñes E.: "Computing with the completed set of intervals: SIGLA-PL/I System" Proc. 22th Science Week, Damascus 1982 (to appear).