IEEE have revised their referencing style.  The updated style can be found on our subject guides at https://isguides.hw.ac.uk/ld.php?content_id=31489650

The key difference is when you use et al.  IEEE uses et al. in reference lists when items have many authors: you should now use et al. if an item has six or more authors (rather than three or more.)

The updated style also includes instructions on how to reference more types of online resources, including eBooks, journal articles and conference proceedings.