Assertion: citric acid's effect | /r/HasProperty | repeated under selective pressure
Facets:
value: many times
type: TEMPORAL
Source sentences:
text: The authors point out in a subsequent publication, which studies the mechanism (Tamura, Schimmel 2006), that such a 4-fold effect, repeated under selective pressure many times, can lead to an overwhelming preference for an L-amino acid in a biological system.