 Two major versions of the BCA exist and were known in Tibet, one much shorter than the other. It was the longer version, of about a thousand verses, that was regarded as canonical in Tibet (see Butön 2013: 259); this longer version is the one most often cited and translated today. Some highly respected scholars (including Harrison in his 2007) argue that the shorter version of about seven hundred verses, sometimes known as the Bodhisattva-caryāvatāra or BsCA, was written first, followed by the ŚS. Later on, someone, probably Śāntideva himself but possibly another author, added the additional verses to form the BCA as we know it now. This chronology makes sense and is supported by some evidence, but we may never know for sure whether it is correct.