An explanation is given here: <a href="http:&#x2F;&#x2F;scaapt.org&#x2F;archives&#x2F;1286" rel="nofollow">http:&#x2F;&#x2F;scaapt.org&#x2F;archives&#x2F;1286</a><p>&gt; &quot;You may ask why the series is being retired. The original producers (Intelecom) do not have the staff or the information available to locate all the third party rights holders of the additional footage and rights to that footage has expired. Therefore, it must be taken out of distribution.&quot;<p>I imagine that unless unknown rights-holders pull them off YouTube (as they apparently haven&#x27;t yet...) then it will still be available some places.<p>The above page also notes the availability of <a href="https:&#x2F;&#x2F;www.learner.org&#x2F;courses&#x2F;physics&#x2F;" rel="nofollow">https:&#x2F;&#x2F;www.learner.org&#x2F;courses&#x2F;physics&#x2F;</a> which includes 11 videos.