Similarly, Lee(2018) analyzed multiple populations in NGC6752 by using Ca-CN photometry and confirmed that the two main groups of CN-weak and CN-strong stars that he identified along the RGB follow the same radial distribution within $\sim$8.2 arcmin from the cluster center.

In the upper panel of Fig. \[fig:pratio1\] we plot the ratio of population-A, B, and C stars against the radial distance from the cluster center by using results from literature and from this paper. The present investigation, which is based on a field with radial distance between 3.3 and 6.6 arcmin from the center of NGC6752, corroborates the conclusion that the three populations of NGC6752 are consistent with a flat radial distribution.

Dependence of multiple populations from stellar mass
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Published studies on multiple populations in NGC6752 are mostly focused on RGB and bright MS stars, which are more massive than $\sim$0.6$\mathcal{M}_{\odot}$. Specifically, results by Milone et al.(2013, 2017) are based either on [*HST*]{} photometry of MS stars with $19.05<m_{\rm F814W}<20.15$ or on photometry of RGB stars from [*HST*]{} and from the Str${\rm \ddot{o}}$mgren catalogue by Grundahl et al.(2002) obtained from New-Technology-Telescope data. The conclusion by Nardiello et al.(2015) are inferred from photometry of MS stars with $19.25<V<20.51$.

The 