| stable(adjective, strain, firmness, safe, labour) |
| strong(adjective, strain, firmness, safe, unaffected) |
| firm(adjective, strain, firmness, safe, labour) |
| sound(adjective, strain, perfect, firmness, safe) |
| resistant(adjective, strain, resist, firmness, safe) |
| proof(adjective, strain, resist, firmness, labour) |
| refractory(adjective, strain, firmness, labour, hardiness) |
| robust(adjective, strain, firmness, labour, hardiness) |
| steady(adjective, strain, firmness, safe, labour) |
| protected(adjective, secure, perfect, safe, unaffected) |
| fast(adjective, strain, firmness, safe, labour) |
| impregnable(adjective, strain, firmness, safe, labour) |
| resilient(adjective, strain, firmness, unaffected, labour) |
| resist(adjective, strain, firmness, labour, hardiness) |
| rigid(adjective, strain, firmness, labour, hardiness) |
| tight(adjective, strain, firmness, safe, unaffected) |
| tolerant(adjective, strain, firmness, labour, hardiness) |
| unyielding(adjective, strain, firmness, labour, hardiness) |
| safe(adjective, secure, perfect, safe, intact) |
| exempt(adjective, clear, free, allow, responsibility) |