Yevamot 27: The Strength of Bonds

A case where chalitzah is expected, but the man gives a get instead -- or where there's a yibum betrothal (ma'amar). Consider the layering of procedure and requirement that clouds the question of the practice at the Torah level of requirement. Also, the case of 2 sisters who had been married to two brothers, with one brother remaining to dispatch the yibum requirement. With a focus on Rav's opinion, and whether he contradicts himself.