Where joined with another Blessing: Rosh Berachot 1:13
"Hashem/Melech Ha'Olam"
And the Mental Focus of the Blessing: Berachot 12a
Validity of a Blessing which omits Hashem/Melech: Tos. Berachot 12a #2
Having an Extra Beginning/Closure [of "Baruch"]
In General: Pesachim 104b
In Blessings on Enjoyment: Pesachim 104b, Ketuvot 7b
In Blessings on Mitzvos: Pesachim 104b
For a Blessing which is adjacent to another: Pesachim 104b
For the last Blessing by Shema: Pesachim 104b
For "HaTov VeHaMaytiv" in Blessings after Meals: Pesachim 104b
Where it is a single "Thanks": (Rashi) Ketuvot 7b
Where it is for a "Matter of Holiness": Ketuvot 7b
Where there is an interruption during the Blessing: (Rashi) Ketuvot 7b
Having a Closure which is similar to the opening, separate from the body of the Blessing: Pesachim 104a
For Havdalah: Pesachim 104b
Other Issues of Structure
Establishing that two different existent versions of a Blessing should be used in combination: Megillah 21b; Taanit 7a