The point in this article is well made and well illustrated in the embedded video - if you choose to watch it be aware it features 18-rated scenes of gore.
Peeping Tom and Psycho also need referencing in any slasher history, as does Last House on the Left and Texas Chainsaw Massacre.
http://nofilmschool.com/2017/02/how-one-most-influential-horror-films-all-time-made-slashers-possible
