As he says that..

As Ballard (2017) states that nicotine is more dangerous than alcohol.

OK so there is a group of reporting verbs that may be followed by that (+ independent clause), while there are others that don’t work with that:

Reporting verbs with ‘that’

  • Henderson (2013) writes that the double quantum matrix is a myth.
  • In 2015 it was discovered by Smith that elephants are more afraid of snakes than mice.
  • The findings of Jones et al. (2017) suggest that music education can lead to more general improvements in academic ability.

Reporting verbs without ‘that’

  • Henderson (2013) describes the double quantum matrix as a myth.
  • In his 2015 study of elephants, Smith identified a discrepancy between fear of mice and fear of snakes.
  • Jones’ research (2017) highlighted improvements in academic ability following music study.

As + that (?!)

This third category simply does not exist! As does not belong with that, so in our opening example we need either:

  • Ballard (2017) states that nicotine is more dangerous than alcohol.

OR..

  • As Ballard (2017) states,┬ánicotine is more dangerous than alcohol.

Indonesian flag But NEVER:

  • As Ballard (2017) states that nicotine is more dangerous than alcohol.