Weiping, 

I also find it annoying when I can’t access certain material. 

However, ‘choosing material that is accessible the whole world over’ is virtually impossible to implement -  copyright law, embargoes on use or a country’s laws etc can all forbid access or publication of a vast array of material based on a broad range of criteria. Not all of these can be known or tested in advance - and unless the restrictions are specifically stated, checking every piece of material for some form of ‘geo-blocking’, would be prohibitive, even if it were possible.

Taken from another perspective, why should other subscribers be subjected to the impacts of these restrictions when they would not otherwise apply to them ?

I do think it should be made clear that the site uses external links and cannot guarantee all material is accessible to all subscribers for a variety of legal and technical reasons. As there is a free trial possible, people can then try the site with knowledge of the limitations, and decide for themselves if it is still worth subscribing.