Beregning af lange sporisolationer. [Xerox ts.re technical aspects of railway signalling / J. Steffensen, March 1952. 24p. in Danish, + 19 xerox technical drawings. Part of the Lascelles collection (chiefly books and periodicals now in the Science Museum Library - see weekly accessions lists 2328 & 2329 of Aug 1975) re railway signalling. See also inv. nos. 2001-297 and 2001-296]