Can you explain the oxygen dissociation curve? and the Bohr Shift?

As each O2 molecule binds to the haemoglobin, it alters the shape of the protein --> making subsequent binding more favourable. Therefore the affininity for oxygen will be greater in places with a higher oxygen concentration (i.e. the lungs) and a lower affinity in places where the oxygen concentration is lower (i.e. in muscles). This explains why the adult oxygen dissociation curve is sigmoidal (or S shaped). Would then draw a diagram to explain the Bohr effect on an oxygen dissociation curve