Chern-Simons modified gravity models in 4-dimensions are shown to be special cases of low energy effective string models to first order in the string constant.
@article{arxiv.0807.1832,
title = {String-Inspired Chern-Simons Modified Gravity In 4-Dimensions},
author = {M. Adak and T. Dereli},
journal= {arXiv preprint arXiv:0807.1832},
year = {2012}
}