A. A. Turbayne - Monograms and Ciphers, 1912.
A monogram is a combination of two or more letters, in which one letter forms part of another and cannot be separated from the whole. A cipher is merely an interlacing or placing together of two or more letters, being in no way dependent for their parts on other of the letters.
The styles included may be classed under five principal heads - Roman, Gothic, Sans Serif, Cursive or Running, and what we might call Rustic. Here and there throughout the work a design will be found that may suggest a treatment for some particular device. There are three principal forms of treating a device; the Imposed, Extended, and the Continuous forms. By the Imposed form we mean a design where the letters are written or interlaced directly over one another. In the Extended form the letters are interlaced or written side by side, and in the Continuous form the device runs from beginning to end without a break.