Space Viking - E-book at ManyBooks. - http://manybooks.net/titles/piperhother06space_viking.html
Oomphel In The Sky - E-book at ManyBooks. - http://manybooks.net/titles/piperhother06Oomphel.html
Lone Star Planet - E-book at ManyBooks. - http://manybooks.net/titles/piperhother06Lone_Star_Planet.html
Time and Time Again - Ernest Kinoy's adaptation for NBC radio program "X Minus One": audio stream at SciIFi.com, Seeing Ear Theatre. - http://www.scifi.com/set/classics/t2/
Four-Day Planet - E-book at ManyBooks. - http://manybooks.net/titles/piperhother06Four-Day_planet.html
The Cosmic Computer - Also published as "Junkyard Planet": e-book at ManyBooks. - http://manybooks.net/titles/piperhother06cosmiccomputer.html
The Return - Collaboration between Piper and John Joseph McGuire: e-book at Project Gutenberg, as published in The Science-Fictional Sherlock Holmes. - http://www.gutenberg.org/etext/19158
Time Crime - E-book at Project Gutenberg. - http://www.gutenberg.org/etext/18151
Temple Trouble - E-book at Project Gutenberg. - http://www.gutenberg.org/etext/18861
Rebel Raider - Historical fiction set in the American Civil War: e-book at Project Gutenberg. - http://www.gutenberg.org/etext/19194
Police Operation - E-book at Project Gutenberg. - http://www.gutenberg.org/etext/19067
Operation R.S.V.P. - E-book at Project Gutenberg. - http://www.gutenberg.org/etext/18261
Null-ABC - Collaboration between Piper and John Joseph McGuire: e-book at Project Gutenberg. - http://www.gutenberg.org/etext/18346
Naudsonce - E-book at Project Gutenberg. - http://www.gutenberg.org/etext/19076
Murder in the Gunroom - E-book of mystery novel at Project Gutenberg. - http://www.gutenberg.org/etext/17866
The Mercenaries - E-book at Project Gutenberg. - http://www.gutenberg.org/etext/18814
Little Fuzzy - E-book at Project Gutenberg. - http://www.gutenberg.org/etext/18137
Genesis - E-book at Project Gutenberg. - http://www.gutenberg.org/etext/18105
Day of the Moron - E-book at Project Gutenberg. - http://www.gutenberg.org/etext/18949
Graveyard of Dreams - E-book at Project Gutenberg. - http://www.gutenberg.org/etext/18109
The Keeper - E-book at Project Gutenberg. - http://www.gutenberg.org/etext/19338