Thank you so much for your reply.

I've used STAN for some analyses. In the paper describing these analyses is it ok for me to say "STAN models consist of flows and stock described by equations (mass balances of the processes, sum of imports, sum of exports, sum of stocks and sum of change in stocks) and variables (import flows, export flows, stocks, change in stocks, sum of imports, sum of exports, sum of stocks and sum of change in stocks). The number of equations and variables in a model depends on the number of processes and flows (import and export)."

Thank you again for your advice.

Wish you a good day.

Best,

Megha