A mishnah with the case of a husband who gives his wife a get with a stipulation that she will be divorced as long as you doesn't go on to marry someone she isn't allowed to marry anyway (her father, his father, and so on). Plus, a case of a husband who gives his wife a get with the stipulation that she doesn't marry someone where the marriage would take hold, but it's still prohibited (like a divorcee to a kohen). Also, a mishnah that delves into the essence of the get, and divorce altogether - the severance of the bond between the husband and wife.