deletions | additions       diff --git a/12 vs 13 [1].tex b/12 vs 13 [1].tex  index 43091ad..c756e61 100644  --- a/12 vs 13 [1].tex  +++ b/12 vs 13 [1].tex 
...
\section{\textsuperscript{12}CO compared to \textsuperscript{13}CO}  One of the key assumptions made is that the gas is optically thin. This holds for 12CO, ^{13}CO,  which is signficantly rarer than 12CO, ^{12}CO,  but it is unclear whether it holds for 12CO. ^{12}CO.  To analyse 12CO we either need to show that it is optically thin, or develop a correction if it is optically thick. \subsection{\textsuperscript{12}CO is optically thick}