Fixing some details and doctests.

Author: tscrim

src/doc/en/reference/references/index.rst

@@ -4779,9 +4779,9 @@ REFERENCES:
               of polynomial maps. Proc. London Math. Soc., 68 (1994), 225-263.
 
 .. [Motsak2006] Olekasandr Motsak. *Computation of the central elements and
-				centralizers of sets of elements in non-commutative polynomial
-				algebras*. PhD Thesis, 2006.
-				https://kluedo.ub.rptu.de/frontdoor/deliver/index/docId/2308/file/Thesis.pdf
+                centralizers of sets of elements in non-commutative polynomial
+                algebras*. PhD Thesis, 2006.
+                https://kluedo.ub.rptu.de/frontdoor/deliver/index/docId/2308/file/Thesis.pdf
 
 .. [MP2019] \M. Montes, D. Penazzi
             "Yarara and Coral v1"

src/sage/algebras/lie_algebras/poincare_birkhoff_witt.py

@@ -577,7 +577,7 @@ def center(self):
 
             sage: g = lie_algebras.Heisenberg(GF(3), 4)
             sage: U = g.pbw_basis()
-            sage: Z = U.center()
+            sage: U.center()
             Center of Universal enveloping algebra of Heisenberg algebra of rank 4
              over Finite Field of size 3 in the Poincare-Birkhoff-Witt basis
         """

src/sage/categories/lie_algebras.py

@@ -356,7 +356,7 @@ def center_universal_enveloping_algebra(self, UEA=None):
                 sage: L.center_universal_enveloping_algebra()
                 Center of Universal enveloping algebra of Abelian Lie algebra on 3 generators (x0, x1, x2)
                  over Rational Field in the Poincare-Birkhoff-Witt basis
-                sage: PBW = L.PBW_basis()
+                sage: PBW = L.pbw_basis()
                 sage: L.center_universal_enveloping_algebra(PBW)
                 Center of Universal enveloping algebra of Abelian Lie algebra on 3 generators (x0, x1, x2)
                  over Rational Field in the Poincare-Birkhoff-Witt basis

src/sage/rings/polynomial/plural.pyx

@@ -856,7 +856,7 @@ cdef class NCPolynomialRing_plural(Ring):
 
         return new_NCP(self,_p)
 
-    def algerbra_generators(self):
+    def algebra_generators(self):
         r"""
         Return the algebra generators of ``self``.
 
@@ -865,9 +865,10 @@ cdef class NCPolynomialRing_plural(Ring):
             sage: A.<x,y,z> = FreeAlgebra(QQ, 3)
             sage: P = A.g_algebra(relations={y*x:-x*y}, order = 'lex')
             sage: P.algebra_generators()
-            (x, y, z)
+            Family (x, y, z)
         """
-        return self.gens()
+        from sage.sets.family import Family
+        return Family(self.gens())
 
     def ideal(self, *gens, **kwds):
         """