Afghanistan   2 studies
Albania   2 studies
Algeria   8 studies
American Samoa   2 studies
Andorra   2 studies
Angola   1 study
Argentina   785 studies
Armenia   1 study
Australia   1993 studies
    Australia, Australian Capital Territory   63 studies
    Australia, New South Wales   841 studies
    Australia, Northern Territory   11 studies
    Australia, Queensland   551 studies
    Australia, South Australia   492 studies
    Australia, Tasmania   78 studies
    Australia, Victoria   923 studies
    Australia, Western Australia   529 studies
Austria   1248 studies
Bahamas   7 studies
Bahrain   2 studies
Bangladesh   53 studies
Barbados   1 study
Belarus   32 studies
Belgium   1978 studies
Belize   2 studies
Benin   6 studies
Bermuda   1 study
Bolivia   9 studies
Bosnia and Herzegovina   35 studies
Botswana   18 studies
Brazil   1154 studies
Bulgaria   325 studies
Burkina Faso   32 studies
Cambodia   12 studies
Cameroon   17 studies
Canada   5418 studies
    Canada, Alberta   1586 studies
    Canada, British Columbia   1560 studies
    Canada, Manitoba   742 studies
    Canada, New Brunswick   341 studies
    Canada, Newfoundland and Labrador   426 studies
    Canada, Nova Scotia   851 studies
    Canada, Ontario   3591 studies
    Canada, Prince Edward Island   99 studies
    Canada, Quebec   2127 studies
    Canada, Saskatchewan   627 studies
Central African Republic   4 studies
Chile   415 studies
China   990 studies
Colombia   249 studies
Congo   10 studies
Congo, The Democratic Republic of the   3 studies
Costa Rica   99 studies
Croatia   248 studies
Cuba   5 studies
Cyprus   15 studies
Czech Republic   952 studies
Côte D'Ivoire   6 studies
Denmark   1665 studies
Dominican Republic   38 studies
Ecuador   49 studies
Egypt   111 studies
El Salvador   8 studies
Estonia   245 studies
Ethiopia   11 studies
Fiji   6 studies
Finland   807 studies
Former Yugoslavia   4 studies
France   3734 studies
Gabon   18 studies
Gambia   25 studies
Georgia   23 studies
Germany   4395 studies
Ghana   37 studies
Greece   584 studies
Guadeloupe   2 studies
Guatemala   89 studies
Guinea   3 studies
Guinea-Bissau   26 studies
Haiti   9 studies
Honduras   14 studies
Hong Kong   331 studies
Hungary   830 studies
Iceland   40 studies
India   840 studies
Indonesia   78 studies
Iran, Islamic Republic of   152 studies
Iraq   2 studies
Ireland   346 studies
Israel   1720 studies
Italy   2487 studies
Jamaica   11 studies
Japan   1019 studies
Jordan   13 studies
Kazakhstan   8 studies
Kenya   67 studies
Korea, Democratic People's Republic of   1 study
Korea, Republic of   997 studies
Kuwait   7 studies
Latvia   210 studies
Lebanon   61 studies
Liberia   1 study
Lithuania   251 studies
Luxembourg   27 studies
Macedonia, The Former Yugoslav Republic of   28 studies
Madagascar   8 studies
Malawi   40 studies
Malaysia   226 studies
Mali   42 studies
Malta   12 studies
Martinique   2 studies
Mauritania   1 study
Mauritius   2 studies
Mexico   885 studies
Moldova, Republic of   7 studies
Monaco   1 study
Montenegro   2 studies
Morocco   28 studies
Mozambique   21 studies
Myanmar   1 study
Nepal   11 studies
Netherlands   2217 studies
Netherlands Antilles   1 study
New Zealand   455 studies
Nicaragua   3 studies
Niger   2 studies
Nigeria   18 studies
Northern Mariana Islands   1 study
Norway   1015 studies
Oman   1 study
Pakistan   103 studies
Panama   70 studies
Papua New Guinea   4 studies
Paraguay   5 studies
Peru   347 studies
Philippines   274 studies
Poland   1376 studies
Portugal   495 studies
Puerto Rico   891 studies
Qatar   8 studies
Romania   532 studies
Russian Federation   990 studies
Rwanda   8 studies
Réunion   2 studies
Saudi Arabia   60 studies
Senegal   16 studies
Serbia   138 studies
Serbia and Montenegro   60 studies
Seychelles   1 study
Sierra Leone   1 study
Singapore   484 studies
Slovakia   433 studies
Slovenia   130 studies
South Africa   862 studies
Spain   2189 studies
Sri Lanka   9 studies
Sudan   5 studies
Swaziland   1 study
Sweden   1292 studies
Switzerland   1450 studies
Syrian Arab Republic   1 study
Taiwan   1230 studies
Tanzania   69 studies
Thailand   463 studies
Togo   1 study
Trinidad and Tobago   4 studies
Tunisia   58 studies
Turkey   458 studies
Uganda   82 studies
Ukraine   377 studies
United Arab Emirates   18 studies
United Kingdom   3323 studies
United States   37270 studies
    United States, Alabama   3440 studies
    United States, Alaska   224 studies
    United States, Arizona   3452 studies
    United States, Arkansas   1851 studies
    United States, California   10465 studies
    United States, Colorado   3568 studies
    United States, Connecticut   2649 studies
    United States, Delaware   880 studies
    United States, District of Columbia   2368 studies
    United States, Florida   6875 studies
    United States, Georgia   4380 studies
    United States, Hawaii   863 studies
    United States, Idaho   806 studies
    United States, Illinois   6168 studies
    United States, Indiana   3642 studies
    United States, Iowa   2030 studies
    United States, Kansas   2259 studies
    United States, Kentucky   2403 studies
    United States, Louisiana   2742 studies
    United States, Maine   769 studies
    United States, Maryland   7279 studies
    United States, Massachusetts   6001 studies
    United States, Michigan   4652 studies
    United States, Minnesota   3929 studies
    United States, Mississippi   1188 studies
    United States, Missouri   4498 studies
    United States, Montana   971 studies
    United States, Nebraska   2110 studies
    United States, Nevada   1521 studies
    United States, New Hampshire   916 studies
    United States, New Jersey   3998 studies
    United States, New Mexico   1287 studies
    United States, New York   9177 studies
    United States, North Carolina   5936 studies
    United States, North Dakota   899 studies
    United States, Ohio   6474 studies
    United States, Oklahoma   2317 studies
    United States, Oregon   2897 studies
    United States, Pennsylvania   7188 studies
    United States, Rhode Island   1463 studies
    United States, South Carolina   3186 studies
    United States, South Dakota   752 studies
    United States, Tennessee   4166 studies
    United States, Texas   8874 studies
    United States, Utah   2066 studies
    United States, Vermont   947 studies
    United States, Virginia   3597 studies
    United States, Washington   4243 studies
    United States, West Virginia   841 studies
    United States, Wisconsin   2931 studies
    United States, Wyoming   218 studies
Uruguay   26 studies
Uzbekistan   1 study
Venezuela   68 studies
Vietnam   46 studies
Zambia   41 studies
Zimbabwe   16 studies