The authors apologise that within the above article, Marath, N., & Subramanian, G. (2018), the image used for figure 5b was incorrect.
The correct image is as below:
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Figure 5. (b) The orbital drift is plotted against C/(C + 1) for an oblate spheroid of aspect ratio 0.1 for various values of λ. The drift does not change sign for an oblate spheroid.