Source: https://www.researchgate.net/profile/Christianna_Williams/publication/253436330_SYMPUT_and_SYMGET_Getting_DATA_Step_Variables_and_Macro_Variables_to_Share/links/0a85e53cd57ac679f4000000/SYMPUT-and-SYMGET-Getting-DATA-Step-Variables-and-Macro-Variables-to-Share.pdf