tian ˩˧ ˧˩
What do these back to back tones mean?
book should be here: book
The reversed tone letter is apparently one of the Modifier Tone Letters which do indeed indicate tone sandhi. I haven't yet come up with a pdf, but hazarding a guess, perhaps ˩˧ (low rising) is the recitation form and the reversed form is the sandhi form (low falling).