IPUMS CPS personal income components classification

I am trying to get CPS personal data from ipums website. However, I am unable to classify personal income components into relatively small groups. I read a research paper named "Big Bad Banks? The Winners and Losers from Bank Deregulation in the United States) by Beck et. al (2010). The authors said the CPS classified different personal income components into three types: wage and salary income (earnings), proprietor income, income from other sources. I wonder what variable in ipums website belongs to these three types, especially the proprietor income. Is proprietor income same as the total of INCBUS and INCFARM?

The comparability section of the INCTOT variable gives the lists of variables uses to construct total personal income for each sample. I am not sure how the authors defined “proprietor income” but it seems safe to guess that INCBUS andINCFARM provide the information they are referring to. Earnings income is captured in the variable INCWAGE. The “other sources” could mean all or some combination of the remaining variables on the list of INCTOT components linked above.

I hope this helps.