Not sure if the citation info is correct, but the URL is.
It's unclear what the difference between s-underdot and s-caron-underdot (p. 23) is supposed to be.
Foster's /x j/ are [x j] word-initially and [ɾ ɽ] word-medially. Since /x/ can also occur word-medially in loanwords, we take the word-medial allophones as underlying here.