I am an SLP and thought that this was a good article to share. My DS was born at 32 weeks and he had issues with feeding, however, the Dr. and NICU nurses would not listen to me about his NG tube/bottle feeding.
The article is somewhat technical but you should be able to follow it:
https://www.asha.org/Publications/leader/2010/100608/Feeding-Skills-Infant.htm
Re: feeding issues in preterm infants-article