Yevamos 5:6-6:1

Yevamos 5:6                                                                             

If the man performed chalitzah and then performed maamar, gave a get or consummated the relationship, or if he consummated the relationship, performed maamar or gave a get and then performed chalitzah – either way, nothing follows chalitzah. This is true whether chalitzah is performed first, last or in the middle. If he consummates the relationship, that’s yibum and nothing follows it; if he does so in the middle or at the end, something else can follow it. Rabbi Nechemya says that consummation and chalitzah are the same – whether they are performed at the beginning, middle or end, nothing else follows it.

Yevamos 6:1                          

If a man had sexual relations with his deceased brother’s widow, whether he did so intentionally or unintentionally, willingly or under duress, even if he participated unintentionally and she participated intentionally or vice versa, he under duress and she willingly or vice versa, full consummation or only partial consummation – in all of these cases, yibum is fulfilled. There is also no distinction between intercourse performed in a “natural” or “unnatural” orifice.