@inproceedings{Appel:1967:TNQ,
  optnote = {},
  optaddress = {},
  optorganization = {},
  author = {Arthur Appel},
  optkey = {},
  optannote = {},
  optseries = {},
  editor = {Solomon Rosenthal},
  url = {http://doi.acm.org/10.1145/280811.280916},
  localfile = {papers/Appel.1967.TNQ.pdf},
  publisher = {Thompson Books},
  doi = {http://doi.acm.org/10.1145/806007},
  optmonth = {},
  citeseer = {http://citeseer.nj.nec.com/context/292841/0},
  optcrossref = {},
  booktitle = {Proceedings of the 22\textsuperscript{nd} ACM National Conference
               1967 (Washington, D.C., USA)},
  optvolume = {},
  optnumber = {},
  abstract = {Line drawings are the most common type of rendering used to convey
              geometrical description. This is due to the economy of preparing
              such drawings and the great information density obtainable. On a
              pure line drawing, that is where no attempt is made to specify or
              suggest shadows, tone or color, the lines rendered are either the
              intersection curves of surfaces or the contour curves of surfaces.
              The nature of these curves are adequately discussed in the
              literature 1 and in a previous report.2 In order to convey a
              realistic impression of an object or an assembly of objects, the
              segments of lines which cannot be seen by an observer are not
              drawn or are drawn dashed. Without specification of visibility a
              drawing is ambiguous. This paper presents a recently developed
              scheme for the determination of visibility in a line drawing which
              enables comparitively high speed calculation and excellent
              resolution.},
  title = {{T}he {N}otion of {Q}uantitative {I}nvisibility and the {M}achine
           {R}endering of {S}olids},
  year = {1967},
  pages = {387--393},
}