what is the correct title for A (song)

[Konomi]

I'm a huge tag freak, I love to tag everything properly... so, here's my question

how should I tag "A" (found on avex 10th Anniversary Presents avex THE ALBUM)? some sites list it as 「A」, while others use 『A』... which is the correct title?

I would be grateful for an answer from someone who actually owns the CD and therefore could look it up for me thanks in advance.