SIGMA - An interactive message service for the Military Message Experiment. - Robert Stotz; Ronald Tugender; David Wilczynski; Donald Oestreicher (MARK, 1979)

Maintaining order and consistency in multi-access data. - Ronald Tugender (MARK, 1979)

The SIGMA experience - A study in the evolutionary design of a large software system. - David Wilczynski; Ronald Tugender; Donald Obstreicher (MARK, 1979)