Text ( visual ) : unmediated Definition and measurement / Marc Uri Porat. -- [Washington, D.C.] : U.S. Dept. of Commerce, Office of Telecommunications ; Washington, D.C. : For sale by the Supt. of Docs., U.S. Govt. Print. Off. , 1977. -- xvi, 250 p. : ill. ; 27 cm. -- (OT special publication ; 77-12(1) . The information economy). -- "Prepared by the Office of Telecommunications with partial support of National Science Foundation" ; Includes bibliographical references. -- (BA35714040) ; https://ci.nii.ac.jp/ncid/BA35714040 Author Heading(s): Porat, Marc Uri ; United States. Dept. of Commerce. Office of Telecommunications ; National Science Foundation (U.S.). -- Classification(s): LCC : HC110.I5 ; DC : 339.2/0973. -- Subject Heading(s): LCSH : National income -- United States -- Accounting ; LCSH : Input-output tables -- United States ; LCSH : Information services -- Economic aspects -- United States