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Publication of DD121196A5publicationCriticalpatent/DD121196A5/xx
G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
G03B21/00—Projectors or projection-type viewers; Accessories therefor
G03B21/54—Accessories
G03B21/56—Projection screens
G03B21/58—Projection screens collapsible, e.g. foldable; of variable area