Huge thanks to an anonymous contributor who graciously provided scans he had from this Pocketpiece which before had been fully missing. This is just a partial Pocketpiece, covering only the primetime ratings, but it is a great find. Post will be updated should the remaining pages ever be found.
Below is a Nielsen pocketpiece covering the 2nd half of April 1978. It features the Nielsen ratings for all television programs airing in the weeks ending April 16, 1978 and April 23, 1978. The first half of the report includes a full alphabetical list of all programs that aired and their two-week average HH rating/impression. The second half of the report provides HH ratings information for individual telecasts each day.
Source: Nielsen Media Research