MAMMALS IN TIME
from the first synapsid to us · 320 million years on one axis
Free
VERTEBRATES IN TIME
when each group appeared · five hundred million years on one axis
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BASIC PHYSICS FORMULAS
fifteen formulas · every letter explained beneath it
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ANIMALS
the main branches — from comb jellies to chordates · who is actually related to whom
Free
VERTEBRATES
from lamprey to bird · and why "fish" and "reptiles" are not groups
Free
MORSE CODE
26 letters and 10 digits · dot, dash
Free
BICYCLE CLASSES
frame, wheel by ISO 5775 and handlebar — three signs of a class, and what the frame is rated for
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CAR CLASSES
segments A to F by length and bodies by box count — how to name any car you see
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