@article{MM2_1993__81_3-4_155899,
     author = {Nanqing Ding and Jianlong Chen},
     title = {Relative coherence and preenvelopes.},
     journal = {Manuscripta mathematica},
     pages = {243--262},
     publisher = {mathdoc},
     volume = {81},
     number = {3-4},
     year = {1993},
     zbl = {0802.16023},
     url = {http://geodesic.mathdoc.fr/item/MM2_1993__81_3-4_155899/}
}