Reaction between Salicylaldehyde and 2-Benzoylpyridine

In a paper by Sheng et al (10.1016/j.dyepig.2018.07.036) the authors synthesize the compound MZC as shown in the scheme below. 
[![Reaction scheme](https://i.stack.imgur.com/M8OzB.png)](https://i.stack.imgur.com/M8OzB.png)


I'm looking for information about what the reaction mechanism is that underpins this reaction. If anyone can share some insights it is much appreciated.


In the experimental section it is written 



> 
> 2-Benzoylpyridine (4 mmol, 0.732 g) and ammonium acetate (22 mmol, 1.70 g)
>  was dissolved in acetic acid (30 mL) and followed by the addition of salicylaldehyde
>  (6 mmol, 0.733 g). The reaction was refluxed for 6 h. The resulting solution mixture
>  was cooled to room temperature and cold water was then added to the mixture. The
>  solid was collected by filtration and washed with a small amount of cooled water,
>  which was purified via recrystallization using acetonitrile to give MZC (0.687 g, 60 %
>  yield). 
> 
> 
> 


