Since some electronic resources are available through different providers (e.g. HighWire or ProQuest), the different links represent an access to the resource given by a different provider.
All links give access to the same resource, however, the interface, type of access (e.g. possibility to download a chapter) and functionalities can vary between providers.
However, when it comes to electronic journals, every link may have a different coverage. It is important to read to Database / Coverage column to make sure the chosen link has the issue you are looking for (e.g. 1964-present or 1996-2012).