how can you indicate in a chemical equation that a reaction is reversible

A reversible reaction can be simply indicated by showing a double arrow in between the reactants and the products... or by two arrows facing in opposite directions placed on top of one another in between the reactants and products.
by double arrow I mean an arrow which indicates both forward and backward mechanism in a reaction i.e. the reaction is reversible in nature and the products can break down or rejoin into the reactants.

p.s. in case you don't understand the two arrows on top of each other comment... open a Microsoft word document... type 21CB and then press ALT+X... the double arrow will appear... :)