some fixes in docstrings

src/callbacks_step/save_solution.jl

@@ -2,13 +2,13 @@
 # https://github.com/trixi-framework/Trixi.jl/blob/cd097fc9d1fe80fb4d7824968d54c99bf3bd5281/src/callbacks_step/save_solution.jl
 
 """
-SaveSolutionCallback(; interval::Integer=0,
-                       dt=nothing,
-                       save_initial_solution=true,
-                       save_final_solution=true,
-                       output_directory="out",
-                       extra_functions=(),
-                       keys=append!(["itp"], "value_" .* string.(eachindex(extra_functions))))
+    SaveSolutionCallback(; interval::Integer=0,
+                         dt=nothing,
+                         save_initial_solution=true,
+                         save_final_solution=true,
+                         output_directory="out",
+                         extra_functions=(),
+                         keys=append!(["itp"], "value_" .* string.(eachindex(extra_functions))))
 
 Save the current numerical solution in regular intervals in VTK format as a
 Paraview Collection (.pvd). Either pass `interval` to save every `interval` time steps

src/equations.jl

@@ -44,7 +44,7 @@ end
 Libear second-order elliptic equation with matrix `A`, vector `b`, and scalar `c` and right-hand side `f`.
 The elliptic equation is defined as
 ```math
-    \mathcal{L}u = \sum_{i,j = 1}^d a_{ij}(x)\partial_{x_i,x_j}^2u + \sum_{i = 1}^db_i(x)\partial_{x_i}u + c(x)u = f,
+    \mathcal{L}u = -\sum_{i,j = 1}^d a_{ij}(x)\partial_{x_i,x_j}^2u + \sum_{i = 1}^db_i(x)\partial_{x_i}u + c(x)u = f,
 ```
 where `A`, `b` and `c` are space-dependent functions returning a matrix, a vector, and a scalar, respectively.
 

src/nodes.jl

@@ -281,7 +281,7 @@ end
 If `n` is integer, create a [`NodeSet`](@ref) with `n` homogeneously distributed nodes in every dimension each of dimension
 `dim` inside a hypercube defined by the bounds `x_min` and `x_max`. If `n` is a `Tuple` of length `dim`,
 then use as many nodes in each dimension as described by `n`. The resulting `NodeSet` will have
-``n^{\textrm{dim}}`` respectively ``\prod_{j = 1}n_j`` points. If the bounds are given as single values,
+``n^{\textrm{dim}}`` respectively ``\prod_{j = 1}{\textrm{dim}}n_j`` points. If the bounds are given as single values,
 they are applied for each dimension. If they are `Tuple`s of size `dim`, the hypercube has the according bounds.
 If `dim` is not given explicitly, it is inferred by the lengths of `n`, `x_min` and `x_max` if possible.
 """