Sanitary conventions were also concluded between European states. A Soviet-Latvian sanitary convention was signed on 24 June 1922, for which ratifications were exchanged on 18 October 1923. A bilateral sanitary convention was concluded between the governments of Latvia and Poland on 7 July 1922, for which ratifications were exchanged on 7 April 1925. Another was concluded between the governments of Germany and Poland in Dresden on 18 December 1922, and entered into effect on 15 February 1923. Another one was signed between the governments of Poland and Romania on 20 December 1922. Ratifications were exchanged on 11 July 1923. The Polish government also concluded such a convention with the Soviet government on 7 February 1923, for which ratifications were exchanged on 8 January 1924. A sanitary convention was also concluded between the governments of Poland and Czechoslovakia on 5 September 1925, for which ratifications were exchanged on 22 October 1926. A convention was signed between the governments of Germany and Latvia on 9 July 1926, for which ratifications were exchanged on 6 July 1927.. How many months after a Soviet-Latvian sanitary convention was signed were the ratifications exchanged?