Finding People with PHDs in CPS

Hello, I am trying to use IPUMS CPS to find people who hold PhDs in Chemistry. It seems that the variable EDUC99 provides information on people who have a doctoral degree post 1991. Is there a variable that clearly defines having a PhD pre-1991? I see that HIGRADE has years of education but I am a little concerned with equating having more years in college meaning having a PhD.

Any suggestions are welcome.



Nevermind, I found the answer myself!