Introduction.md

@@ -48,4 +48,7 @@ References
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 [Freeman. *et al.,* (2017)](https://doi.org/10.1002/joc.4775) 
-Freeman, E., Woodruff, S.D., Worley, S.J., Lubker, S.J., Kent, E.C., Angel, W.E., Berry, D.I., Brohan, P., Eastman, R., Gates, L., Gloeden, W., Ji, Z., Lawrimore, J., Rayner, N.A., Rosenhagen, G. and Smith, S.R. (2017), ICOADS Release 3.0: a major update to the historical marine climate record. Int. J. Climatol., 37: 2211-2232. doi:10.1002/joc.4775
+Freeman, E., Woodruff, S.D., Worley, S.J., Lubker, S.J., Kent, E.C., Angel, W.E., Berry, D.I., Brohan, P., Eastman, R., Gates, L., Gloeden, W., Ji, Z., Lawrimore, J., Rayner, N.A., Rosenhagen, G. and Smith, S.R. (2017), ICOADS Release 3.0: a major update to the historical marine climate record. Int. J. Climatol., 37: 2211-2232. doi:10.1002/joc.4775
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+
+[Smith. *et al.,* (2016)](https://icoads.noaa.gov/e-doc/imma/R3.0-imma1_short.pdf) 
+Smith, S.R., Freeman, E., Lubker, S.J., Woodruff, S.D., Worley, S.J., Angel, W.E., Berry, D.I., Brohan, P., Ji, Z. and Kent, E.C., 2016. The International Maritime Meteorological Archive (IMMA) Format. Unpublished document.
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