Need to find those pesky Rakata Energy Cubes?   You need four of these to get the Green matrix Shard datacron on Belsavis.   Luckily, you only need four for a group, each person doesn't need to have them.

These are the most common and reliable locations.  There a few outside The Tomb, but the spawns are rare.

Location A:

Location B:

Location C:

Location D:

Location E:

Location F:

Location G:

Location H: