Brian Stableford makes a related point about Lost Worlds: "The motif has gradually fallen into disuse by virtue of increasing geographical knowledge; these days lost lands have to be very well hidden indeed or displaced beyond some kind of magical or dimensional boundary. Such displacement [...] so transforms their significance that they are better thought of as Secondary Worlds or Otherworlds."  In two linked entries by editor John Clute, the encyclopedia distinguishes "Otherworld" from its subclass "Secondary World", and also from the settings of Supernatural Fiction and Planetary Romance, and from related concepts.</ref>