Meaning of G.S.R and S.O ?????

sharath (ca) (42 Points)

31 July 2018  
"Amendment in the notification number G.S.R. 463(E) dated the 5th June, 2015 vide Notification no. S.O. 802(E) dated 23rd February, 2018"


whats the meaning of GSR and S.O in this????