I have html code:
<input type="checkbox" name="true[1][]" value="1">
<input type="checkbox" name="true[1][]" value="2">
<input type="checkbox" name="true[1][]" value="3">
...
<input type="checkbox" name="true[2][]" value="1">
<input type="checkbox" name="true[2][]" value="2">
<input type="checkbox" name="true[2][]" value="3">
...
How can I set minimum one required for checkboxes with same name? For example: minimum one required for group true[1][], minumum one required for group true[2][].
It should be without JS =) Only HTML.