Eating it if one isn't related to the Mourner: Moed Katan 24b
Eating it in the road, after the burial: Ketuvot 8b
Eating this meal for the death of a Torah Scholar even though there is no blood relationship: Shabbat 105b, Moed Katan 25a
Eating this meal for the death of a good person: Moed Katan 25a
Eating this meal if one is present at the death of any person: Moed Katan 25a
How it is Eaten
Serving Utensils: Moed Katan 27a
The mourner may not eat his own bread on the first day: Moed Katan 27b
Eating the food of another mourner: Moed Katan 27b
The non-mourners sit on an upright bed: Moed Katan 24b, 26b
The above is not so if the consolers are close with the mourners: Moed Katan 26b
How this meal is served to a King: Moed Katan 27a