Analog Science Fiction - Science Fact December 1968 (Volume 82, Number 4)
Illustrations by Kelly Freas, Leo Summers. Cover by Kelly Freas (for "The Custodians.")

Novelettes: "The Custodians" by James H. Schmitz (a "Hub" story)
"The Reluctant Ambassadors" by Stanley Schmidt
"Pipeline" by Joe Poyer.

Stories: "A Learning Experience" by Theodore Litwell
"The Form Master" by Jack Wodhams.

Science: "Situation of Some Gravity" by Joseph F. Goodavage.

John W. Campbell's editorial is "Technological Status"; Book reviews by P. Schuyler Miller.