The Siva Sutras is based on a 9th century root text attributed to Vasugupta. As far as we know, it now only exists embedded in various commentaries written in the 10th and 11th centuries. The two most commonly available in English are: this work -- 1. The Siva Sutras: The Yoga of Supreme Identity test of the Sutras with the Commentary Vimarshini of Kshemaraja (10th Century C.E.) which has been translated into English by Jaideva Singh and Swami Lakshman Joo,

and #2 the commentary called the The aphorisms of Śiva : the ŚivaSūtra with Bhāskara's commentary, the Vārttika Bhaskara (11th century C.E.) which has been translated into English by Mark Dyczkowski.

The ancient commentaries make up a large portion of each work and different from each other substantially. To make matters more confusing there are other versions of the Siva Sutras embedded in different ancient commentaries. Use extreme caution when considering what to combine.