| certify(verb, support, accept, maintain, agree) |
| endorse(verb, support, accept, agree) |
| guarantee(verb, support, maintain, back, declare) |
| substantiate(verb, support, maintain, back, declare) |
| support(verb, accept, maintain, agree, back) |
| vouch for |
| acknowledge(verb, support, agree, verbally) |
| act as a witness(verb, expression, idiom, support, maintain) |
| affirm(verb, support, maintain, back, declare) |
| approve(verb, support, accept, agree, idea) |
| assert(verb, support, maintain, back, declare) |
| asseverate(verb, support, maintain, back, declare) |
| authenticate(verify, validate) |
| avert(verb, support, maintain, back, declare) |
| avow(verb, support, maintain, back, declare) |
| back(verb, support, maintain, declare, confirm) |
| be responsible for(verb, support, maintain, back, declare) |
| bear out(expression, verify, validate, authenticate) |
| bear testimony(verb, expression, support, maintain, back) |
| check up(verb, expression, phrasal verb, idea, confirm) |