Excel formulae to use different worksheets i.e worksheet 4, can use worksheet 1, 2 0r 3

Question

I have a workbook. WorkBook contains 4 worksheets. On the 4 th worksheet, i would like it to have functionality to be using different worksheets i.e worksheets 1,2 or 3 as reference for calculations.workbook with 4 worksheets, 3 are references for values on 4 th worksheet