Search for causing mutations is very laborious, time consuming and low effective.

We continued a few miles farther, walking being very laborious without snow-shoes.

We continued a few miles further, walking being very laborious without snowshoes.

Saddled with these heavy burdens, the party found the return journey very laborious.

I bore the fatigue of the walk, which was very laborious, without inconvenience.

That trip was a very laborious one on account of the sluggish tide.

The duties of that Committee, when I was upon it, were very laborious.

Carving is here a very laborious employment, for the knives are never whetted.

It is a very laborious, hot and hard way to can.

Then he proceeded to pack up his belongings, not a very laborious affair.

On the contrary, they are very laborious, and singularly uncareful for their personal comfort.

But the duties of his profession were very laborious: they could not be neglected.

It is remarkable, therefore, that he was very laborious in his method of work.

Why did you undertake that very laborious task you mention?

Well named for travel very laborious during this time.

I found chopping, in the summer months, very laborious.