http://www.med.umich.edu/yourchild/topics/devmile.htm
http://www.ldonline.org/article/6313
https://www.education.com/reference/article/acquisition-sentence-forms/
http://www.speech-language-therapy.com/index.php?option=com_content&view=article&id=35:admin&catid=2:uncategorised&Itemid=117
http://www.speech-language-therapy.com/index.php?option=com_content&view=article&id=34:ages&catid=11:admin&Itemid=117
http://www.speech-language-therapy.com/index.php?option=com_content&view=article&id=33:brown&catid=2:uncategorised&Itemid=117
Sound Development Chart
Phonological Processes Chart