Sorry for a dumb question but I cannot get this right.

I have a workbook with multiple worksheets, lets say the sheet names are
Summary, Jan, Feb etc. In sheet 'Summary' in cell A1 I have the name of one
of these sheets, let's say A1 =Jan.

In cell A3 (of 'Summary') i want the contents of cell B2 of sheet Jan
displayed.

I have the following formula in cell A3 (of 'Summary') =INDIRECT(A1&"!B2")
but I get a REF error back.

Please help