Here is a link to the text of Resolution 1296 (1968). Not sure how much of this already exists, but this resolution would have goverened the WTS's application.
I did some fishing around at the UN site and came up with some interesting statements about the requirments for NGOs. Here is one and, again, note the dates:
"Non-governmental organizations that have consultative status with the Economic and Social Council are required to report every four years on the work they did supporting the United Nations, as governed by guidelines set in Council resolution 1296 (XLIV) of May 1968. After examining the reports, the Committee may recommend to the Council any appropriate reclassification in the status of the organizations concerned. "
"In 1968, the Economic and Social Council, by Resolution 1297 (XLIV) of 27 May, called on DPI to associate NGOs, bearing in mind the letter and spirit of its Resolution 1296 (XLIV) of 23 May 1968, which stated that an NGO "...shall undertake to support the work of the United Nations and to promote knowledge of its principles and activities, in accordance with its own aims and purposes and the nature and scope of its competence and activities".
clearly suggests that the 1968 ESOC resolution would apply to NGO's associated through the DPI. Thus the two catagories are clearly linked.