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There is wonderful example of mutual understanding between scientists all over the world. The picture of Space Shuttle and necessity of modeling of plume from the vapor of Tunguska comet were presented in the booklet by A.E.Zlobin "Tunguska meteorite problem on the threshold of XX century", Moscow, CIAM, 1996, 28 pages. Also there is good correspondence to A.E.Zlobin's conclusion concerning water ice as the most of substance of Tunguska comet (2007 Planetary Defense Conference).

One more confirmation on cometary origin of Tunguska explosion. We agree that Tunguska explosion was accompanied with chemical reactions and these reactions was a part of total energy of explosion. But we do not mean this part as considerable large. The paper is very important, but it will be useful for authors to read papers of russian research group directed by M.N.Tsinbal and V.E.Shnitke. These authors described chemical aspects of Tunguska explosion in 1988. Also we must remind, that russian scientists investigated Tunguska catastrophe during 100 years. Unfortunately we did not find any reference to these giant work. Certainly, we not agree to the speed 30 km/sec and the mass 5·10⁷ kg for Tunguska comet. Also we consider dubious that Cheko lake was formed by considerable fragment of Tunguska comet.

We are glad to state, that scientific initiatives of CIAM (Moscow) on quasi 3-D modeling of Tunguska Comet Impact (A.E.Zlobin, 1988-1996) has real confirmation with another scientific organizations. In accordance to 3-D simulation of Sandia National Laboratories (Mark Boslough and colleagues, December 17, 2007) an explosion "was more likely only three to five megatons". This estimation of energy is in good correspondence to A.E.Zlobin's paper in Planetary Defense Conference - 2007 (March 5-8) "Quasi Three-dimensional Modeling of Tunguska Comet Impact (1908)". As A.E.Zlobin declare in this paper, energy of blast of comet's biggest fragment "A" was ~5.5 megatons (2.4·10¹⁶ J). However, we would like to notice, that comet origin and ice substance of Tunguska space body is not confirmed by Sandia National Laboratories till now.

This research paper contain estimation of heat impulse associated with the Tunguska explosion. Minimum heat impulse estimated by authors of this research paper as 25 J/cm2. This estimation is in good correspondence to results by A.E.Zlobin (13 - 30 J/cm2). However upper limit of heat impulse, mentioned by authors of the paper, seems to be unreal (300 J/cm2). Authors of the paper does not take into consideration features of heating of ground at the region of Tunguska catastrophe. For example, A.E.Zlobin has calculated with FEM not only heating of branch of trees but also heating of ground surface. As stated by A.E.Zlobin (solution of 2-D partial equation of heat conduction), it is necessary to take into consideration heat conduction during calculations too. It is necessary to remind that A.E.Zlobin has investigated influence of heat impulse and thermal damages of vegetation's sediments directly in the site of Tunguska catastrophe. For this purpose he made more than ten prospect-holes in the peat-bogs during expedition of 1988. It became possible for A.E.Zlobin to compare view of real thermal influence in the site and results of accurate calculated heat impulse (2-D FEM). It must be noted that authors of the paper "The Tunguska Event in 1908: Evidence from Tree-Ring Anatomy" mentioned references, connected to incorrect so-called "eastern" trajectory. But in general, we consider the paper as interesting and perspective, and support further investigation of heat impulse of Tunguska explosion by high qualified experts.

The article contain objective information concerning situation in science. We very glad that important information about Tunguska comet danger became accessible for people of Vietnam.

The same information is presented here concerning Tunguska and concerning real situation in science. There is only one mistake in this article. Size of hard fragment of the Tunguska comet is not equal 10 centimeters.