Subject: What are the different ways to write/abbreviate nucleotides?

I have seen the same nucleotide written in 3 different ways, and I would like 
to know the guidelines and rules for writing them in all 3 ways.

For example:  I have seen 'thymidine dinucleotide' written as pTpT, p(dT)2, and 
a 3rd way that was written using a 5' and 3'(I cant remember the exact way, but 
I remember the 5' and 3' with some stuff in between).  pTpT, I pretty much 
understand.  p(dT)2, I think I know(except for the d?).  The 3rd way I have no 
clue.

Re: What are the different ways to write/abbreviate nucleotides?