Abbreviation for "this study"
As already indicated in my comment, you can use a symbol such as an asterisk to denote the work at hand. Then, explain the meaning of this symbol in the table caption where you should have the space therfor.
As already indicated in my comment, you can use a symbol such as an asterisk to denote the work at hand. Then, explain the meaning of this symbol in the table caption where you should have the space therfor.