Bibliography for Vitkir + Mead in Sacrifice Reference?

[Jachra]

I noticed there wasn't a bibliography entry for the Vitkir.

Specifically, I'm trying to find out if this is an invention of the authors or from a source:

It is said that in ancient times the gods new how to brew a potion from raw vis, mead, herbs, blood, and other more-exotic materials that would allow a person to survive the ordeal by placing him in a comatose state for nine days, during which time he would appear to be dead. If a character manages to discover the recipe, he will experience strange visions during the ritual, and does not need to apply Wound or Fatigue penalties to his Concentration roll. When he awakens from unconsciousness, he must recover all of his Fatigue levels as if from long-term fatigue. The strength of the potion also gives him a bonus to his Concentration of +1 for every pawn of vis used to brew it. However, once the ritual is complete, he must also roll one botch die for each pawn, as if he had botched a roll, and any 0s represent permanent physical or mental Flaws.
Such potions are not easy to brew, and according to the legends they usually require seeking out one of the gods or the alfar (pronounced “ALF-ar,” roughly meaning “the elves”) for mystical insight into the appropriate ingredients for a given person. Traditionally, this advice always comes with a price. Ingredients might include mythical concepts such as the breath of a fsh, stubble from a woman’s beard, the promise of a liar, or the ears of a bird.
Often the potion must be accompanied by a blood oath, a solemn vow to serve the gods however they command. Such an oath is very dangerous, for commands from the gods are usually on the scale of nearly-suicidal heroic quests.

I figure this is just an elaborate reference to the Mead of Poetry, but I wanted to be sure.