PHASES OF THE MOON
eight phases · a full cycle of 29.53 days
$1.50
THE SOLAR SYSTEM
eight planets · size, distance, year and day
Free
MORSE CODE
26 letters and 10 digits · dot, dash
Free
PHONETIC ALPHABET
the ICAO standard · for radio and telephone
$2.50
SI PREFIXES
from quetta to quecto · twenty multipliers
$1.50