Republicans are seeking the public testimony of Vice President Joe Biden’s son, Hunter, as well as the anonymous whistleblower when the House holds public impeachment proceedings next week.

Rep. Devin Nunes of California, the top Republican on the House Intelligence Committee, requested the witnesses in a letter to committee Chairman Adam Schiff on Saturday morning.

Schiff is likely to refuse many of the witness requests, and as the chairman, Schiff has the power to block any witnesses from testifying under a resolution setting out the rules that the House voted on earlier this month.

“Americans see through this sham process despite the Democrats’ efforts to retroactively legitimize it last week,” Nunes wrote to Schiff.

[Also read: Schiff signals he will reject GOP 'sham' witness requests]

The GOP list includes eight witnesses, as well as “all individuals relied upon by the anonymous whistleblower in drafting his or her secondhand complaint.”

Democrats are seeking to impeach the president because they believe he used his office to try to coerce Ukraine to investigate Biden and Democratic interference in the 2016 election. The process began after an anonymous whistleblower received secondhand information about a July 25 phone call between Trump and Ukraine’s president and filed a complaint.

On the call, Trump asked President Volodymyr Zelensky to investigate corruption involving former Vice President Joe Biden as well as the Democratic National Committee.

Republicans have put forward a witness list aimed at proving Trump had a good reason to be seeking Ukraine’s help investigating corruption.

Trump wanted Ukraine to pledge to investigate Biden’s effort while he was vice president to fire a prosecutor in Ukraine who had been targeting gas company Burisma Holdings, which was paying Hunter Biden a hefty salary.

Republicans are seeking the testimony of Devon Archer, a former board member of Burisma Holdings. And they have requested the testimony of Alexandra Chalupa, a former Democratic National Committee staffer who Republicans said worked with the Ukrainian Embassy in Washington, D.C., “to try to get political dirt on then-candidate Trump’s campaign.”

Republicans are seeking witnesses who provided closed-door depositions to lawmakers over the past several weeks.

The list includes Ambassador Kurt Volker, who served as a special envoy to Ukraine. Nunes has requested Volker serve on the same panel as acting Ambassador William Taylor, who testified behind closed doors that he believes Trump was trying to force Ukraine to investigate the Bidens in exchange for critical security aid.

Republicans also want to hear from David Hale, the undersecretary of state for political affairs, and Tim Morrison, senior director for European and Russian affairs on the National Security Council.

Morrison said in closed-door testimony that he did not believe Trump did anything wrong in his July 25 conversation with Zelensky.