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, nicotine is more dangerous than alcohol.

Indonesian flag But NEVER:

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

Using ‘that’ to acknowledge sources

A study conducted in 1965 identified that argument mapping leads to clearer writing.

Some reporting verbs require a ‘that’ clause, others do not:

  • A study conducted in 1965 showed that argument mapping leads to clearer writing.
  • A study conducted in 1965 identified improvements to writing following argument mapping.

Reporting verbs not followed by that are usually followed by a noun phrase. Unfortunately there is no strategy to determine which verbs require that and which do not. You just have to memorise them. The best way to acquire useful reporting verbs is by reading journal articles and academic text books. To get you started, here is a list of common reporting verbs followed by that:

admit agree argue assume
believe claim conclude consider
decide deny determine discover
doubt explain hypothesize imply
indicate infer maintain prove
presume reveal show state

Chomsky (2014) argued (or argues?)

Chomsky (2014) argued that grammar monopoly is an effective way to highlight first language interference.

I know, I know. 2014 is past and finished, so you want to use past simple tense. However, in this case the currency of the idea – is it recent and/or valid? – is more important than when it was written.

The currency of an idea can occasionally be difficult to determine, but in most cases it is obvious. If we assume that Chomsky is still alive (as he is at the time of this writing) and that his idea is still current then we use present simple tense, even if the idea was written in the finished past:

  • Chomsky (2014) argues that Grammar Monopoly is an effective way to highlight first language interference.

In most postgraduate writing we are dealing with current ideas, from recent sources, and so most of the time you will need present tense for your reporting verbs.