the series begins with "intervention: a root tale to the galactic milieu and a vinculum between it and the saga of pliocene exile" (, boston: houghton mifflin, 1987). this was released in one volume in the uk, but in mass market paperback in the usa as two volumes: "surveillance" and "metaconcert". may calls "intervention" a "vinculum", or link-tale, between the "saga of pliocene exile" and the milieu trilogy proper. however, it is a near-essential introduction to the milieu trilogy as well as a balanced stand-alone work.