I mean which method you use to complete the dataset at your location? Or you simply use the nearest station with long dataset of tritium in precipitation? I am a bit sceptical of extrapolating into past as i do not know how big the tritium peak actually was.
But on the other hand my city (Ljubljana, Slovenia) is near Vienna, so I guess that for the period 1961-1972 I could use Vienna dataset. The argument for these is also that there is a 0.99 correlation coefficient for these period between Vienna (Austria) and Ottawa (Canada) dataset. I hope you understand what I am asking. Thank you.