✓  1500s (1)
 •  1600s
 •  1700s
 ✓  1800s (31)
 ✓  1900-1929 (36)
 ✓  1930-1949 (9)

 •  1950-1969
 •  1970s
 ✓  1980s (8)
 ✓  1990s (51)
 ✓  2000s (22)

 ✓  Argentina (3)
 •  Australia
 •  Austria
 •  Belarus
 ✓  Belgium (1)
 •  Brazil
 •  Canada
 •  Chile
 ✓  Croatia (7)
 •  Cuba
 •  Denmark
 •  Ecuador
 ✓  Egypt (10)
 •  Ethiopia
 ✓  Finland (11)
 ✓  France (2)
 ✓  Germany (3)
 •  Greece
 •  Hungary
 •  India
 ✓  Iran (1)
 •  Ireland
 ✓  Israel (1)
 •  Italy
 ✓  Jamaica (11)
 ✓  Japan (6)
 •  Kenya
 ✓  Lebanon (1)
 •  Lithuania
 •  Macedonia
 •  Malaysia
 •  Malta
 ✓  Mexico (4)

 •  Mongolia
 •  Nepal
 ✓  Netherlands (1)
 ✓  New Zealand (12)
 •  Nicaragua
 •  Norway
 •  Palestine
 •  Peru
 •  Philippines
 •  Poland
 •  Portugal
 •  Scotland
 •  Russia
 •  Rwanda
 •  Serbia and Montenegro
 ✓  Singapore (6)
 •  Slovakia
 •  Slovenia
 •  South Africa
 •  Spain
 •  Sri Lanka
 •  Sweden
 ✓  Switzerland (10)
 ✓  Syria (3)
 •  Tanzania
 •  Turkey
 •  Ukraine
 •  United Arab Emirates
 ✓  United Kingdom (15)
 ✓  United States (85)
 •  Yugoslavia
 ✓  Zimbabwe (1)

 ✓  Three Star Rating (3)
 ✓  Four Star Rating (32)

 ✓  Five Star Rating (23)

 ✓  Animals (40)
 ✓  Plants (4)
 •  Fossils and Rocks
 •  Land and Water

 ✓  Weather and Seasons (5)
 •  Space and Astronomy
 •  Human Body and Health