Reference for Yevamot 42:17
ולטעמיך שיבסרי הויין דהא איכא אשת אחי האם מן האם דפשטינן לאיסורא הא לא קשיא
'I saw the [list of] forbidden relatives of the second degree of Mar the son of Rabana<span class="x" onmousemove="('comment',' Or Rabina. ');"><sup>42</sup></span> and sixteen were written down as forbidden cases. Would they not be the eight of the Baraitha,<span class="x" onmousemove="('comment',' Supra 21a. ');"><sup>43</sup></span> the six of the School of R. Hiyya,<span class="x" onmousemove="('comment',' Infra 22a. ');"><sup>44</sup></span> and these two,<span class="x" onmousemove="('comment',' Those of Amemar, agreed to by R. Ashi. V. supra p. 128. n. 20. ');"><sup>45</sup></span> in all sixteen? — But according to your view there should be seventeen, since there is also the case of the wife of a mother's maternal brother, who in accordance with our decision is forbidden!' — 'This is no difficulty.