Length-Based Methods II: Gale and Church, 1993
The algorithm uses sentence length (measured in characters) to evaluate how likely an alignment of some number of sentences in L1 is with some number of sentences in L2.
The algorithm uses a Dynamic Programming technique that allows the system to efficiently consider all possible alignments and find the minimum cost alignment.
The method performs well (at least on related languages). It gets a 4% error rate. It works best on 1:1 alignments [only 2% error rate]. It has a high error rate on more difficult alignments.