Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
G09F—DISPLAYING; ADVERTISING; SIGNS; LABELS OR NAME-PLATES; SEALS
G09F19/00—Advertising or display means not otherwise provided for
G09F19/12—Advertising or display means not otherwise provided for using special optical effects
G09F19/18—Advertising or display means not otherwise provided for using special optical effects involving the use of optical projection means, e.g. projection of images on clouds
Theoretical and Practical Graphics: An Educational Course on the Theory and Practical Applications of Descriptive Geometry and Mechanical Drawing, Prepared for Students in General Science, Engineering Or Architecture