Decimal classification and rocket: what they have in common

1. Step 1. Decimal classification — uses — Library catalogue. Classifying the collection.
2. Step 2. Library catalogue — has part — Index card. Cards.
3. Step 3. Index card — is made of — Paper. Paper.
4. Step 4. Paper — is material for — Rocket. The first rockets were paper tubes filled with gunpowder.

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