Hello Joy!

I'm not sure what stage/level you are at in your studies.

There is a very good book that is simply written called, Introducing Psychology - Developmental Psychology published by Grange Books which leads you through the developmental stages.

It really depends on the level you are doing. Whether it is just a simple essay or requires doing your own research? Either way I suggest that you do some research on the net and read as much as you can on the subject and incorperate you own learning experiences. Are you currently working with older people? Getting it from the horses mouth always helps too.

Sorry if I have misread what you are requiring, I wish you luck!