Hi Michael! S401-29.8 looks like a reference found in the CIS Annual Indexes (print volumes that index the publications of Congress). In the 1978 CIS Index, S401-29.8 maps to a Senate Committee on Governmental Affairs hearing titled Act to Combat International Terrorism on the Omnibus Anti-terrorism Act of 1977. The Sudoc number for the hearing is Y4.G74/9:T27 if you'd like to look for a copy in your local Federal Depository Library.
I understand this isn't a House Appropriations hearing -- can you contact us over at firstname.lastname@example.org so we can get some more information on what you're looking for? We're happy to help you figure it out. Thanks!