Is it possible for twins to have different fathers?

Dear Deus,
Twins, [two babies] produced from one pregnancy result from a woman shedding two eggs which implant in the womb after fertilisation.
These are called fraternal twins. Twins can also result from a fertilised egg breaking into two forming identical twins.
Fraternal twins can result from sperms from two different men (heteropaternal superfecundation) fertilizing two different eggs. Also sperms from two different acts of sex from the same man can lead to twins but this may be more difficult to prove by DNA testing.
Usually to avoid a woman who is pregnant, from having another egg fertilised, ovulation does not take place.
Fertilisation takes place in the fallopian tubes but it takes a few days (6-10 days) for the fertilised egg to implant.
Sometimes before implantation, during the six-day fertility window, another egg may be shed raising a possibility of the two different eggs being fertilised by sperms from different men if a woman has had sex with different men then.
Also sperms can last up to five days in the fallopian tubes and a woman having had sex with different men may have a mix of sperms from different men in the fallopian tubes awaiting ovulation and fertilisation.