The phrase "according to a systematic" is not correct as it is incomplete and lacks a noun to follow "systematic." You can use it when referring to a systematic approach or method, but it needs to be part of a complete thought.
Example: "According to a systematic review of the literature, the findings suggest a need for further research."
Alternatives: "based on a systematic" or "in line with a systematic".
The parity values are determined according to a systematic real convolution code.
Lung ultrasound was performed according to a systematic protocol in supine patients.
According to a systematic review, mean prevalence of membrane perforation was 19.5%% [6].
The beaches were sampled in winter 1996 and summer 1997 according to a systematic design with stratification.
The estimated female-to-male ratio of MS incidence increased from 1.4 in 1955 to 2.3 in 2000, according to a systematic review of 28 epidemiologic studies [2].
The review of academic literature referred to the wheat to bread chain is developed according to a systematic approach (Fink, 2014; Pfau et al., 2014).
According to a systematic review, depression occurred independently of most tumor- or treatment-related variables, including brain tumor type, histologic grade, location, or various treatment modalities [6].
The physical mechanisms of the degradation as well as the different defects involved have been discussed according to a systematic set of experiments with different stress conditions.
According to a systematic review of the literature, membrane bioreactors (MBRs) are still actively investigated in the field of wastewater treatment.
According to a systematic review of clinical studies on psychopathology in children and adolescents with migraine, there is no evidence that attention problems and externalizing symptoms are more frequent in this group compared with headache free controls [38].
According to a systematic review by Kleindienst and colleagues (2005), depression-mania episode sequence, earlier onset of illness, a high number of previous hospitalizations, and continuous cycling seem to be associated with poor outcomes.
