Sources:

http://sociopages.wikispaces.com/Earth+as+a+Planet
http://www.limaesrock.com/tag/season/
https://mbc-items-production.s3.amazonaws.com/items/documents/016/021/880/original/Reason%20for%20the%20Seasons%20Notes.pdf?AWSAccessKeyId=AKIAJE3X3RZJLUZQKLMQ&Expires=1410292713&Signature=LE%2B2RdZGwAS2DytzxPv2OAKyPcM%3D&response-content-type=application%2Fpdf
http://www.thewilltochoose.com/?attachment_id=65
http://funcram.com/pictures/four-seasons-in-a-single-picture.html
www.universetoday.com
Why do we have seasons packet (general)