COFECHA Tip #6: If no reference chronology is handy, and you have many undated measurement series, first see if you have internal dating among them. These should all be measured beginning with year "0" or year "1." When asked to enter a dated series, hit return. Next, enter the name of the file containing the undated series, when prompted. COFECHA will then test each series against all others. Look for t-values at or above 3.5!