The scientist has written about important events. (Present Perfect)
The scientist had written about important events. (Past Perfect)
The scientist will have written about important events. (Future Perfect)
Ученый написал о важных событиях. (Present Perfect)
Ученый написал о важных событиях. (Past Perfect)
Ученый напишет о важных событиях. (Future Perfect)
The scientist has written about important events. (Present Perfect)
The scientist had written about important events. (Past Perfect)
The scientist will have written about important events. (Future Perfect)
Ученый написал о важных событиях. (Present Perfect)
Ученый написал о важных событиях. (Past Perfect)
Ученый напишет о важных событиях. (Future Perfect)