@misc{1166196,
  author = {William C Cullen and William W Walton},
  title = {The soiling characteristics of structural masonry units ::report},
  year = {1961},
  month = {1961-01-01 05:01:00},
  publisher = {, National Institute of Standards and Technology, Gaithersburg, MD},
  doi = {https://doi.org/10.6028/NBS.RPT.7065},
  language = {en},
}