Complex sentence: Richmond-based writer Shane Lambert said that many of the shoes found were manufactured and sold in 2004 or earlier, and that there could be other sources for the shoes or multiple sources.
Split into simpler sentences: Richmond-based writer Shane Lambert has advocated this position, pointing to the fact that many of the shoes found were manufactured and sold in 2004 or earlier. Lambert acknowledges that there could be other sources for the shoes or multiple sources.