Reference for Niddah 127:37

ה"מ היכא דקיימא בתוך ימי נדתה אבל היכא דלא קיימא בתוך ימי נדתה אימא לא קמ"ל

present an objection against Samuel?<span class="x" onmousemove="('comment',' Who maintains that no settled period in arithmetical progression can be established unless the discharge appeared on three dates exclusive of the first. ');">³⁴</span>

Jastrow