(CNN) The impeachment inquiry into President Donald Trump has left quite a paper trail, which started with a whistleblower complaint about Trump's interactions with the President of Ukraine, led to the White House releasing its transcript of the phone call in question and extends with each new subpoena issued by House Democrats to examine whether Trump abused his office.

We've assembled links to the key official documents for you to keep track of the unfolding story yourself.

The whistleblower complaint

The anonymous whistleblower complaint from a member of the intelligence community included a letter to the chairmen of both the House and Senate intelligence committees that said Trump tried to get Ukraine to interfere in the 2020 election. The letter , dated August 12, 2019, was declassified and released on September 26.

We know it can be hard to keep up with the daily twists and turns around the impeachment inquiry. We boil it down to the essentials and send it to your inbox.

Nancy Pelosi's letter to Congress about the whistleblower

After the existence of the whistleblower became known -- but before the complaint was released -- House Speaker Nancy Pelosi sent a letter to her colleagues imploring the Trump administration to allow the whistleblower to come before Congress.

The Trump-Ukraine phone call transcript

After days of speculation about what actually was said during Trump's July 25 phone call with Ukrainian President Volodymyr Zelensky, the White House gave in to Democratic demands and released a rough -- not word-for-word -- transcript of the conversation.

Intelligence community inspector general's letter about the whistleblower complaint

The internal watchdog for the intelligence community sent a letter to acting Director of National Intelligence Joseph Maguire on August 26, two weeks after the whistleblower complaint was received by the inspector general's office. The inspector general wrote that "there are reasonable grounds to believe" that the whistleblower complaint constitutes an "urgent concern" under the law.

Whistleblower's attorney expresses 'serious concerns'

A lawyer for the whistleblower cited Trump's statements to express his concerns that "our client will be put in harm's way."

House Democrats subpoena Rudy Giuliani

House Democratic committee chairmen Adam Schiff, Eliot Engel and Elijah Cummings issued a subpoena on September 30 to Trump's personal lawyer Rudy Giuliani for documents related to Ukraine as part of the House impeachment inquiry.

Damning text messages released

House Democrats released text messages between US and Ukrainian officials that appear to show an understanding that if Ukraine wanted military aid and a visit to Washington, the Ukrainians would need to agree to investigate the origins of the Russia investigation as well as Joe Biden and his son Hunter.

White House subpoenaed

On October 4, House Democrats subpoenaed the White House for documents related to Ukraine, after sending a separate request for documents to Vice President Mike Pence.

White House to Democrats: We 'cannot participate in your partisan and unconstitutional inquiry'

On October 8, the White House told House Democrats that they were seeing to "overturn the results of the 2016 election and deprive the American people of the President they have freely chosen" and the administration will not be cooperating.

Giuliani associates indicted

Two associates of Rudy Giuliani connected to efforts to dig up dirt in Ukraine on Joe Biden were indicted on criminal charges for allegedly funneling foreign money into US elections. They were arrested October 10 at an airport outside Washington.

Giuliani associates subpoenaed

The same day they were indicted, the two Giuliani associates -- Igor Fruman and Lev Parnas -- were subpoenaed by House Democrats.

Rick Perry subpoenaed

House Democrats issued a subpoena October 10 to Energy Secretary Rick Perry for documents related to the Trump administration's contacts with Ukraine as part of the impeachment inquiry.

Giuliani won't give up documents

In a letter to Congress on October 15, Giuliani's attorney said the former New York City mayor will not provide any documents requested by congressional subpoena "because this appears to be an unconstitutional, baseless, and illegitimate 'impeachment inquiry.'"

House impeachment resolution

The House Rules Committee on October 29, unveiled the text of the resolution for the full House to vote on Thursday to formalize impeachment proceedings.

The testimony transcripts

The three House committees leading the impeachment inquiry began releasing transcripts of their closed-door witness testimonies the week of November 4. Read the depositions of:

Whistleblower's attorney asks the President to 'cease and desist'

A lawyer for the Ukraine call whistleblower sent White House counsel Pat Cipollone a letter on November 7 warning Trump to "cease and desist" attacking his client: "Let me be clear: should any harm befall any suspected named whistleblower or their family, the blame will rest squarely with your client."

House Intelligence Committee Democrats release impeachment report

Committee Democrats called evidence of Trump's misconduct and obstruction of Congress "overwhelming" in a new report detailing the allegations against the President involving Ukraine. The 300-page report set the stage for the impeachment of a US president for just the third time in history, but stopped short of outright recommending impeachment, saying that is a decision for Congress to ultimately make.

House Judiciary Committee releases impeachment report

The House Judiciary Committee released a report ahead of its December 9 hearing, laying out historical arguments for impeachment. The report is an update to the Judiciary Committee reports that were issued in 1974 and 1998 during the impeachment proceedings of Presidents Richard Nixon and Bill Clinton.

Articles of impeachment

House Democratic leaders unveiled their articles of impeachment against President Donald Trump on Tuesday, December 10, 2019.

Updates will be added.