[en] The method of two pion interferometry was used to obtain source-size and lifetime parameters for the pions produced in heavy ion collisions. The systems used were 1.70 · A GeV ⁵⁶Fe + Fe, 1.82 · A GeV ⁴⁰Ar + KCl and 1.54 · A GeV ⁹³Nb + Nb, allowing for a search for dependences on the atomic number. Two acceptances (centered, in the lab., at ∼ 0 degrees and 45 degrees) were used for each system, allowing a search for dependences on the viewing angle. The correlation functions were calculated by comparing the data samples to background (or reference) samples made using the method of event mixing, where pions from different events are combined to produce a data sample in which the Bose-Einstein correlation effect is absent. The effect of the correlation function on the background samples is calculated, and a method for weighting the events to remove the residual correlation effect is presented. The effect of the spectrometer design on the measured correlation functions is discussed, as are methods for correcting for these effects during the data analysis. 58 refs., 39 figs., 18 tabs