Which two lines in this excerpt from edgar allan poe's "the raven" show the use of flashback?
once upon a midnight dreary, while i pondered weak and weary,
over many a quaint and curious volume of forgotten lore,—
while i nodded, nearly napping, suddenly there came a tapping,
as of some one gently rapping, rapping at my chamber door.
"'tis some visitor," i muttered, "tapping at my chamber door—
only this, and nothing more."

ah, distinctly i remember it was in the bleak december,
and each separate dying ember wrought its ghost upon the floor.
eagerly i wished the morrow; —vainly i had sought to borrow
from my books surcease of sorrow—sorrow for the lost lenore—
for the rare and radiant maiden whom the angels name lenore—
nameless here for evermore.