Afghanistan   2 studies
Albania   3 studies
Algeria   9 studies
American Samoa   3 studies
Andorra   3 studies
Angola   1 study
Argentina   837 studies
Armenia   3 studies
Australia   2117 studies
    Australia, Australian Capital Territory   69 studies
    Australia, New South Wales   915 studies
    Australia, Northern Territory   12 studies
    Australia, Queensland   586 studies
    Australia, South Australia   523 studies
    Australia, Tasmania   89 studies
    Australia, Victoria   1000 studies
    Australia, Western Australia   560 studies
Austria   1352 studies
Azerbaijan   1 study
Bahamas   6 studies
Bahrain   6 studies
Bangladesh   58 studies
Barbados   1 study
Belarus   39 studies
Belgium   2128 studies
Belize   4 studies
Benin   6 studies
Bermuda   1 study
Bolivia   9 studies
Bosnia and Herzegovina   43 studies
Botswana   21 studies
Brazil   1292 studies
Bulgaria   363 studies
Burkina Faso   34 studies
Cambodia   12 studies
Cameroon   17 studies
Canada   5840 studies
    Canada, Alberta   1673 studies
    Canada, British Columbia   1670 studies
    Canada, Manitoba   786 studies
    Canada, New Brunswick   366 studies
    Canada, Newfoundland and Labrador   435 studies
    Canada, Nova Scotia   903 studies
    Canada, Ontario   3830 studies
    Canada, Prince Edward Island   107 studies
    Canada, Quebec   2303 studies
    Canada, Saskatchewan   647 studies
Central African Republic   4 studies
Chile   442 studies
China   1138 studies
Colombia   278 studies
Congo   10 studies
Congo, The Democratic Republic of the   3 studies
Costa Rica   96 studies
Croatia   279 studies
Cuba   6 studies
Cyprus   16 studies
Czech Republic   1034 studies
Côte D'Ivoire   7 studies
Denmark   1764 studies
Dominican Republic   41 studies
Ecuador   47 studies
Egypt   125 studies
El Salvador   9 studies
Estonia   272 studies
Ethiopia   14 studies
Fiji   6 studies
Finland   868 studies
Former Yugoslavia   7 studies
France   4067 studies
Gabon   19 studies
Gambia   24 studies
Georgia   27 studies
Germany   4784 studies
Ghana   42 studies
Greece   638 studies
Guadeloupe   2 studies
Guatemala   91 studies
Guinea   3 studies
Guinea-Bissau   26 studies
Haiti   10 studies
Honduras   14 studies
Hong Kong   378 studies
Hungary   901 studies
Iceland   43 studies
India   949 studies
Indonesia   86 studies
Iran, Islamic Republic of   172 studies
Iraq   4 studies
Ireland   364 studies
Israel   1891 studies
Italy   2715 studies
Jamaica   13 studies
Japan   1112 studies
Jordan   22 studies
Kazakhstan   12 studies
Kenya   78 studies
Korea, Democratic People's Republic of   2 studies
Korea, Republic of   1147 studies
Kuwait   11 studies
Latvia   229 studies
Lebanon   75 studies
Liberia   1 study
Libyan Arab Jamahiriya   1 study
Lithuania   269 studies
Luxembourg   26 studies
Macedonia, The Former Yugoslav Republic of   34 studies
Madagascar   7 studies
Malawi   44 studies
Malaysia   252 studies
Mali   49 studies
Malta   14 studies
Martinique   2 studies
Mauritania   1 study
Mauritius   2 studies
Mexico   951 studies
Moldova, Republic of   11 studies
Monaco   2 studies
Mongolia   2 studies
Montenegro   4 studies
Morocco   36 studies
Mozambique   23 studies
Myanmar   1 study
Nauru   1 study
Nepal   12 studies
Netherlands   2383 studies
Netherlands Antilles   1 study
New Caledonia   1 study
New Zealand   484 studies
Nicaragua   3 studies
Niger   2 studies
Nigeria   19 studies
Northern Mariana Islands   1 study
Norway   1090 studies
Oman   3 studies
Pakistan   116 studies
Panama   70 studies
Papua New Guinea   4 studies
Paraguay   5 studies
Peru   374 studies
Philippines   295 studies
Poland   1486 studies
Portugal   516 studies
Puerto Rico   936 studies
Qatar   9 studies
Romania   609 studies
Russian Federation   1082 studies
Rwanda   8 studies
Réunion   2 studies
Saint Kitts and Nevis   1 study
Saudi Arabia   71 studies
Senegal   18 studies
Serbia   184 studies
Serbia and Montenegro   43 studies
Seychelles   1 study
Sierra Leone   1 study
Singapore   515 studies
Slovakia   475 studies
Slovenia   146 studies
South Africa   940 studies
Spain   2413 studies
Sri Lanka   12 studies
Sudan   5 studies
Swaziland   1 study
Sweden   1404 studies
Switzerland   1551 studies
Syrian Arab Republic   3 studies
Taiwan   1349 studies
Tanzania   77 studies
Thailand   511 studies
Togo   1 study
Trinidad and Tobago   4 studies
Tunisia   65 studies
Turkey   500 studies
Uganda   88 studies
Ukraine   427 studies
United Arab Emirates   22 studies
United Kingdom   3582 studies
United States   39810 studies
    United States, Alabama   3629 studies
    United States, Alaska   239 studies
    United States, Arizona   3662 studies
    United States, Arkansas   1944 studies
    United States, California   11088 studies
    United States, Colorado   3760 studies
    United States, Connecticut   2816 studies
    United States, Delaware   910 studies
    United States, District of Columbia   2482 studies
    United States, Florida   7302 studies
    United States, Georgia   4585 studies
    United States, Hawaii   894 studies
    United States, Idaho   857 studies
    United States, Illinois   6515 studies
    United States, Indiana   3828 studies
    United States, Iowa   2108 studies
    United States, Kansas   2398 studies
    United States, Kentucky   2561 studies
    United States, Louisiana   2857 studies
    United States, Maine   815 studies
    United States, Maryland   7576 studies
    United States, Massachusetts   6320 studies
    United States, Michigan   4910 studies
    United States, Minnesota   4119 studies
    United States, Mississippi   1243 studies
    United States, Missouri   4776 studies
    United States, Montana   1007 studies
    United States, Nebraska   2221 studies
    United States, Nevada   1590 studies
    United States, New Hampshire   967 studies
    United States, New Jersey   4200 studies
    United States, New Mexico   1353 studies
    United States, New York   9648 studies
    United States, North Carolina   6251 studies
    United States, North Dakota   970 studies
    United States, Ohio   6847 studies
    United States, Oklahoma   2436 studies
    United States, Oregon   3040 studies
    United States, Pennsylvania   7549 studies
    United States, Rhode Island   1544 studies
    United States, South Carolina   3312 studies
    United States, South Dakota   776 studies
    United States, Tennessee   4433 studies
    United States, Texas   9439 studies
    United States, Utah   2192 studies
    United States, Vermont   991 studies
    United States, Virginia   3797 studies
    United States, Washington   4463 studies
    United States, West Virginia   888 studies
    United States, Wisconsin   3071 studies
    United States, Wyoming   128 studies
Uruguay   28 studies
Uzbekistan   1 study
Venezuela   81 studies
Vietnam   49 studies
Zambia   44 studies
Zimbabwe   18 studies