With Soviet aid, a rebuilding program was initiated, an effort that reconstructed the Old Towns of Warsaw and Gdansk, among others, in costly and meticulous efforts based on paintings, photographs and architectural drawings.
The rebuilding of the two areas was completed over a ten year period. 
mnli hypothesis: The rebuilding of the two areas was completed over a ten year period.  premise: With Soviet aid, a rebuilding program was initiated, an effort that reconstructed the Old Towns of Warsaw and Gdansk, among others, in costly and meticulous efforts based on paintings, photographs and architectural drawings.