Hello,

I would like to regress the following equation: DV_{i,c,j,t} = a_i+α_c+α_j+a_t+beta * (IV_i*Dummy_t)+e_{i,c,j,t},

where a_i absorbs certain risk characteristics for industry i, a_c for company characteristics, a_j for country characteristics, and a_t take into account the common trends over time. indicates the relationship between the IV across industries and the Dummy Variable over time and e_{i,c,j,t} will be the error term.
I have observations for the DV, IV, Dummy Variable, and industries (different ISIC codes). For companies and countries, I also have a lot of observations.

This is what I have got so far but I am not sure how to correctly account for the companies, industries, and countries:

tsset Date, daily
reg DV c.IV#i.Dummy

How do I account for the industries, companies, countries with different constants "a"?