# Platt's Notation/Nomenclature for transitions

How do you read Platt's Notation / Nomenclature? Where can I learn this?

Some examples where I've seen this mentioned:

In Platt's notation the transitions are designated as $\ce{A -> B}$ and $\ce{A -> C}$ transitions

The analysis reveals that the $L_a$ and $B_a$ states of the benzene fragments mix with CT configurations

The second $\pi\pi^*$ state has the largest oscillator strength and it is designated as $L_a$, using Platt's nomenclature

$\ce{A -> B}$ seems to refer to the $\ce{\pi -> \pi^*}$, while $\ce{A -> C}$ seems to refer to $n\ce{-> \pi^*}$, but I'm not sure how to read the notation.