Investigation Led by ZnaToKi, or Investigation Led by Experts (Russian: Следствие ведут ЗнаТоКи, translit.

Sledstvie vedut ZnaToKi) was a popular[1][2] 1971-1989 Soviet detective TV-series with two Russian series (2002 and 2003).

Main characters — investigator Pavel Znamenski, detective Alexandr Tomin and laboratory analyst Zinaida Kibrit were acting together under a group name ZnaToKi (translated as "Experts").

The song by Mark Minkov based on the lyrics Invisible Battle (Nezrimiy Boi or Our mission is both dangerous and difficult, and most invisible at first glance...) by Anatoly Gorokhov features in almost all series.

[3] See ru:Категория:Следствие ведут ЗнаТоКи for Russian Wikipedia articles on individual episodes.