The authors prove that a local n-quasigroup defined by the equation $x_{n+1}=F(x₁,...,xₙ)=(f₁\left(x₁\right)+...+fₙ\left(xₙ\right))/(x₁+...+xₙ)$, where $f_i\left(x_i\right)$, i,j = 1,...,n, are arbitrary functions, is irreducible if and only if any two functions $f_i\left(x_i\right)$ and $f_j\left(x_j\right)$, i ≠ j, are not both linear homogeneous, or these functions are linear homogeneous but $f_i\left(x_i\right)/x_i\ne f_j\left(x_j\right)/x_j$. This gives a solution of Belousov’s problem to construct examples of irreducible n-quasigroups for any n ≥ 3.

Si considerano due spazi $S_{\mu }$ e $S_{\nu }^{\ast }$, Riemanniani e a metrica eventualmente indefinita, riferiti a sistemi di co-ordinate $\mathrm{\varnothing }$ e ${\mathrm{\varnothing }}_{\nu }^{\ast }$; e inoltre un doppio tensore $T_{\mathrm{\cdots }}^{\mathrm{\cdots }}$ associato ai punti ${\mathrm{\varnothing }}^{-1}(x)\in S_{\mu }$ e ${\mathrm{\varnothing }}^{\ast -1}(y)\in S^{\ast }$. Si pensa $T_{\mathrm{\cdots }}^{\mathrm{\cdots }}$ dato da una funzione ${\tilde{T}}_{\mathrm{\cdots }}^{\mathrm{\cdots }}$ di $m$ altri tali doppi tensori e di variabili puntuali $x(\in {\mathrm{\Re }}^{\mu })$, $t\in \mathrm{\Re }$ e $y(\in {\mathrm{\Re }}^{\nu })$; poi si considera la funzione composta $${\widehat{T}}_{\mathrm{\cdots }}^{\mathrm{\cdots }}(x,t,y)={\tilde{T}}_{\mathrm{\cdots }}^{\mathrm{\cdots }}[\underset{1,\mathrm{\dots },m}{\underbrace{{\breve{H}}_{\mathrm{\cdots }}^{\mathrm{\cdots }}(x,t,y),\mathrm{\dots },{\breve{H}}_{\mathrm{\cdots }}^{\mathrm{\cdots }}(x,t,y)}},x,t,y].$$ Nella Parte I si scrivono due regole per eseguire la derivazione totale di questa, connessa con una mappa $\widehat{ℰ}$

In this paper some properties of an immersion of two-dimensional surface with boundary into $Esp4$ are studied. The main tool is the maximal principle property of a solution of the elliptic system of partial differential equations. Some conditions for a surface to be a part of a 2-dimensional spheren in $Esp4$ are presented.