1968—Pub. L. 90–252 increased appropriation from $15,000,000 to $25,000,000.

1965—Pub. L. 89–14 increased appropriation from $12,000,000 to $15,000,000.

1963—Pub. L. 88–230 increased appropriation from $7,500,000 to $12,000,000 and amount available for administrative purposes from $1,000,000 to $1,500,000.

1961—Pub. L. 87–273 increased appropriation to $7,500,000 and amount available for administrative purposes to $1,000,000.