Please note that the term, "Terumat Maaser," refers to a tithe which is removed from Maaser Rishon and given to a Kohen.
If someone has declared a gift of a certain of volume maaser to a certain Levi, may that Levi use it for Terumat Maaser before actually receiving it, or must he be concerned lest the owner back out: Bava Metzia 49a
If Terumat Maaser was separated from Tithe taken directly from the grain sheaves before Terumah was taken, that Tithe is usable and free from the Terumah obligation: Shabbat 127b; Eruvin 31b; Pesachim 35b
What happens if someone who is a Tevul Yom says regarding part of his Maaser Rishon, "This portion will become Terumat Maaser at dusk": Eruvin 36a
Approximating the percentage to separate: Beitzah 13b
Whether one who eats Terumat Maaser inappropriately, accidentally, pays for its value and adds one-fifth: Bava Metzia 55b
Whether one who eats Terumat Maaser of produce that may already have been tithed [demai] inappropriately, accidentally, pays for its value and adds one-fifth: Bava Metzia 55b